diff --git a/openassessment/assessment/models/base.py b/openassessment/assessment/models/base.py
index 43243ec66c..ed17272cf8 100644
--- a/openassessment/assessment/models/base.py
+++ b/openassessment/assessment/models/base.py
@@ -19,6 +19,7 @@
 import logging
 import math
 
+import six
 from lazy import lazy
 
 from django.core.cache import cache
@@ -105,7 +106,7 @@ def content_hash_from_dict(rubric_dict):
         rubric_dict.pop("content_hash", None)
 
         canonical_form = json.dumps(rubric_dict, sort_keys=True)
-        return sha1(canonical_form).hexdigest()
+        return sha1(canonical_form.encode('utf-8')).hexdigest()
 
     @staticmethod
     def structure_hash_from_dict(rubric_dict):
@@ -137,7 +138,7 @@ def structure_hash_from_dict(rubric_dict):
             for criterion in rubric_dict.get('criteria', [])
         ]
         canonical_form = json.dumps(structure, sort_keys=True)
-        return sha1(canonical_form).hexdigest()
+        return sha1(canonical_form.encode('utf-8')).hexdigest()
 
 
 class Criterion(models.Model):
@@ -510,7 +511,7 @@ def get_median_score_dict(cls, scores_dict):
 
         """
         median_scores = {}
-        for criterion, criterion_scores in scores_dict.iteritems():
+        for criterion, criterion_scores in six.iteritems(scores_dict):
             criterion_score = Assessment.get_median_score(criterion_scores)
             median_scores[criterion] = criterion_score
         return median_scores
@@ -673,7 +674,7 @@ def create_from_option_names(cls, assessment, selected, feedback=None):
 
         # Validate that we have selections for all criteria
         # This will raise an exception if we're missing any selections/feedback required for criteria
-        cls._check_all_criteria_assessed(rubric_index, selected.keys(), feedback.keys())
+        cls._check_all_criteria_assessed(rubric_index, list(selected.keys()), list(feedback.keys()))
 
         # Retrieve the criteria/option/feedback for criteria that have options.
         # Since we're using the rubric's index, we'll get an `InvalidRubricSelection` error
@@ -684,13 +685,13 @@ def create_from_option_names(cls, assessment, selected, feedback=None):
                 'option': rubric_index.find_option(criterion_name, option_name),
                 'feedback': feedback.get(criterion_name, u"")[0:cls.MAX_FEEDBACK_SIZE],
             }
-            for criterion_name, option_name in selected.iteritems()
+            for criterion_name, option_name in six.iteritems(selected)
         ]
 
         # Some criteria may have feedback but no options, only feedback.
         # For these, we set `option` to None, indicating that the assessment part
         # is not associated with any option, only a criterion.
-        for criterion_name, feedback_text in feedback.iteritems():
+        for criterion_name, feedback_text in six.iteritems(feedback):
             if criterion_name not in selected:
                 assessment_parts.append({
                     'criterion': rubric_index.find_criterion(criterion_name),
@@ -742,7 +743,7 @@ def create_from_option_points(cls, assessment, selected):
                 'criterion': rubric_index.find_criterion(criterion_name),
                 'option': rubric_index.find_option_for_points(criterion_name, option_points),
             }
-            for criterion_name, option_points in selected.iteritems()
+            for criterion_name, option_points in six.iteritems(selected)
         ]
 
         # Add in feedback-only criteria
diff --git a/openassessment/assessment/models/training.py b/openassessment/assessment/models/training.py
index 17e13497c4..a97f5ad84a 100644
--- a/openassessment/assessment/models/training.py
+++ b/openassessment/assessment/models/training.py
@@ -4,6 +4,8 @@
 from hashlib import sha1
 import json
 
+import six
+
 from django.core.cache import cache
 from django.db import models
 
@@ -54,7 +56,7 @@ def create_example(cls, answer, options_selected, rubric):
 
         # This will raise `InvalidRubricSelection` if the selected options
         # do not match the rubric.
-        for criterion_name, option_name in options_selected.iteritems():
+        for criterion_name, option_name in six.iteritems(options_selected):
             option = rubric.index.find_option(criterion_name, option_name)
             example.options_selected.add(option)
         return example
@@ -133,7 +135,7 @@ def calculate_hash(answer, options_selected, rubric):
             'options_selected': options_selected,
             'rubric': rubric.id
         })
-        return sha1(contents).hexdigest()
+        return sha1(contents.encode('utf-8')).hexdigest()
 
     @classmethod
     def cache_key(cls, answer, options_selected, rubric):
diff --git a/openassessment/assessment/test/constants.py b/openassessment/assessment/test/constants.py
index 2fc4d7a8b6..f7927ca9b8 100644
--- a/openassessment/assessment/test/constants.py
+++ b/openassessment/assessment/test/constants.py
@@ -2,6 +2,7 @@
 """
 Constants used as test data.
 """
+import six
 
 STUDENT_ITEM = {
     'student_id': u'𝓽𝓮𝓼𝓽 𝓼𝓽𝓾𝓭𝓮𝓷𝓽',
@@ -76,7 +77,7 @@
         "expected_points": sum(
             RUBRIC_OPTIONS[i]["points"] for i in value
         )
-    } for key, value in OPTIONS_SELECTED_CHOICES.iteritems()
+    } for key, value in six.iteritems(OPTIONS_SELECTED_CHOICES)
 }
 
 EXAMPLES = [
diff --git a/openassessment/fileupload/backends/swift.py b/openassessment/fileupload/backends/swift.py
index 4a222f2dbe..de06404366 100644
--- a/openassessment/fileupload/backends/swift.py
+++ b/openassessment/fileupload/backends/swift.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 '''
 Add in /edx/app/edxapp/edx-platform/lms/envs/aws.py:
 ORA2_SWIFT_URL = AUTH_TOKENS["ORA2_SWIFT_URL"]
@@ -11,10 +12,12 @@
 'swift stat -v' to get it.
 '''
 
+from __future__ import absolute_import, division, print_function, unicode_literals
+
 import logging
-import urlparse
 
 import requests
+from six.moves.urllib.parse import urlparse
 import swiftclient
 
 from django.conf import settings
@@ -96,5 +99,5 @@ def get_settings():
 
     url = getattr(settings, 'ORA2_SWIFT_URL', None)
     key = getattr(settings, 'ORA2_SWIFT_KEY', None)
-    url = urlparse.urlparse(url)
+    url = urlparse(url)
     return key, url
diff --git a/openassessment/workflow/api.py b/openassessment/workflow/api.py
index 2ca1f25c30..df1fb8bd6f 100644
--- a/openassessment/workflow/api.py
+++ b/openassessment/workflow/api.py
@@ -4,6 +4,8 @@
 """
 import logging
 
+import six
+
 from django.db import DatabaseError
 
 from openassessment.assessment.errors import PeerAssessmentError, PeerAssessmentInternalError
@@ -340,7 +342,7 @@ def _get_workflow_model(submission_uuid):
             problem.
 
     """
-    if not isinstance(submission_uuid, basestring):
+    if not isinstance(submission_uuid, six.string_types):
         raise AssessmentWorkflowRequestError("submission_uuid must be a string type")
 
     try:
diff --git a/openassessment/workflow/models.py b/openassessment/workflow/models.py
index 06d166e451..dd6e8ae0ff 100644
--- a/openassessment/workflow/models.py
+++ b/openassessment/workflow/models.py
@@ -58,7 +58,7 @@ class AssessmentWorkflow(TimeStampedModel, StatusModel):
     an after the fact recording of the last known state of that information so
     we can search easily.
     """
-    STEPS = ASSESSMENT_API_DICT.keys()
+    STEPS = list(ASSESSMENT_API_DICT.keys())
 
     STATUSES = [
         "waiting",  # User has done all necessary assessment but hasn't been
diff --git a/openassessment/workflow/test/test_api.py b/openassessment/workflow/test/test_api.py
index 8f9c03c3eb..3d341d3fda 100644
--- a/openassessment/workflow/test/test_api.py
+++ b/openassessment/workflow/test/test_api.py
@@ -46,6 +46,13 @@
 @ddt.ddt
 class TestAssessmentWorkflowApi(CacheResetTest):
 
+    def test_status_values_include_all_steps(self):
+        self.assertIsInstance(AssessmentWorkflow.STEPS, list)
+        self.assertEqual(
+            AssessmentWorkflow.STATUS_VALUES,
+            AssessmentWorkflow.STEPS + AssessmentWorkflow.STATUSES
+        )
+
     @ddt.file_data('data/assessments.json')
     def test_create_workflow(self, data):
         first_step = data["steps"][0] if data["steps"] else "peer"
diff --git a/openassessment/xblock/course_items_listing_mixin.py b/openassessment/xblock/course_items_listing_mixin.py
index 479575c087..e612b3ef09 100644
--- a/openassessment/xblock/course_items_listing_mixin.py
+++ b/openassessment/xblock/course_items_listing_mixin.py
@@ -3,8 +3,12 @@
 
 """
 
+from __future__ import absolute_import
+
 import json
 
+import six
+
 from webob import Response
 from xblock.core import XBlock
 
@@ -26,5 +30,5 @@ def get_ora2_responses(self, request, suffix=''):  # pylint: disable=unused-argu
         """
         # Import is placed here to avoid model import at project startup.
         from openassessment.data import OraAggregateData
-        responses = OraAggregateData.collect_ora2_responses(unicode(self.course_id))
+        responses = OraAggregateData.collect_ora2_responses(six.text_type(self.course_id))
         return Response(json.dumps(responses), content_type='application/json')
diff --git a/openassessment/xblock/data_conversion.py b/openassessment/xblock/data_conversion.py
index f5a395838b..d1b2d21d31 100644
--- a/openassessment/xblock/data_conversion.py
+++ b/openassessment/xblock/data_conversion.py
@@ -2,8 +2,12 @@
 Data Conversion utility methods for handling ORA2 XBlock data transformations and validation.
 
 """
+from __future__ import absolute_import
+
 import json
 
+import six
+
 
 def convert_training_examples_list_to_dict(examples_list):
     """
@@ -85,8 +89,7 @@ def update_assessments_format(assessments):
     for assessment in assessments:
         if 'examples' in assessment and assessment['examples']:
             for example in assessment['examples']:
-                if (isinstance(example, dict) and
-                    (isinstance(example['answer'], unicode) or isinstance(example['answer'], str))):
+                if isinstance(example, dict) and isinstance(example['answer'], six.string_types):
                     example['answer'] = {
                         'parts': [
                             {'text': example['answer']}
diff --git a/openassessment/xblock/grade_mixin.py b/openassessment/xblock/grade_mixin.py
index ce79817cf3..2e715254a0 100644
--- a/openassessment/xblock/grade_mixin.py
+++ b/openassessment/xblock/grade_mixin.py
@@ -1,6 +1,9 @@
+# -*- coding: utf-8 -*-
 """
 Grade step in the OpenAssessment XBlock.
 """
+from __future__ import absolute_import, division, print_function, unicode_literals
+
 import copy
 
 from lazy import lazy
@@ -8,9 +11,10 @@
 
 from django.utils.translation import ugettext as _
 
-from data_conversion import create_submission_dict
 from openassessment.assessment.errors import PeerAssessmentError, SelfAssessmentError
 
+from .data_conversion import create_submission_dict
+
 
 class GradeMixin(object):
     """Grade Mixin introduces all handlers for displaying grades
@@ -410,6 +414,7 @@ def _peer_median_option(self, submission_uuid, criterion):
 
         median_scores = peer_api.get_assessment_median_scores(submission_uuid)
         median_score = median_scores.get(criterion['name'], None)
+        median_score = -1 if median_score is None else median_score
 
         def median_options():
             """
@@ -423,7 +428,7 @@ def median_options():
               5. Options A=1, B=3 and C=5, a median score of 6 returns [C]
                  Note: 5 should not happen as a median should never be out of range.
             """
-            last_score = None
+            last_score = -1
             median_options = []
 
             # Sort the options first by name and then by points, so that if there
@@ -436,7 +441,7 @@ def median_options():
                 current_score = option['points']
 
                 # If we have reached a new score, then decide what to do next
-                if current_score is not last_score:
+                if current_score != last_score:
 
                     # If the last score we saw was already larger than the median
                     # score, then we must have collected enough so return all
@@ -472,7 +477,7 @@ def median_options():
             return options[0]
         return {
             'label': u' / '.join([option['label'] for option in options]),
-            'points': median_score,
+            'points': median_score if median_score != -1 else None,
             'explanation': None,
         }
 
diff --git a/openassessment/xblock/leaderboard_mixin.py b/openassessment/xblock/leaderboard_mixin.py
index fc0c1eecd0..ab571f04ce 100644
--- a/openassessment/xblock/leaderboard_mixin.py
+++ b/openassessment/xblock/leaderboard_mixin.py
@@ -1,6 +1,10 @@
 """
 Leaderboard step in the OpenAssessment XBlock.
 """
+from __future__ import absolute_import
+
+import six
+
 from xblock.core import XBlock
 
 from django.utils.translation import ugettext as _
@@ -94,7 +98,7 @@ def render_leaderboard_complete(self, student_item_dict):
             if 'text' in score['content'] or 'parts' in score['content']:
                 submission = {'answer': score.pop('content')}
                 score['submission'] = create_submission_dict(submission, self.prompts)
-            elif isinstance(score['content'], basestring):
+            elif isinstance(score['content'], six.string_types):
                 pass
             # Currently, we do not handle non-text submissions.
             else:
diff --git a/openassessment/xblock/lms_mixin.py b/openassessment/xblock/lms_mixin.py
index c3ec8fbda6..61e0ae2b41 100644
--- a/openassessment/xblock/lms_mixin.py
+++ b/openassessment/xblock/lms_mixin.py
@@ -2,6 +2,10 @@
 Fields and methods used by the LMS and Studio.
 """
 
+from __future__ import absolute_import
+
+import six
+
 from xblock.fields import DateTime, Dict, Float, Scope, String
 
 
@@ -13,7 +17,7 @@ def from_json(self, access_dict):
 
     def to_json(self, access_dict):
         if access_dict is not None:
-            return {unicode(k): access_dict[k] for k in access_dict}
+            return {six.text_type(k): access_dict[k] for k in access_dict}
 
 
 class LmsCompatibilityMixin(object):
diff --git a/openassessment/xblock/openassessmentblock.py b/openassessment/xblock/openassessmentblock.py
index 460e603b6f..66dc619892 100644
--- a/openassessment/xblock/openassessmentblock.py
+++ b/openassessment/xblock/openassessmentblock.py
@@ -1,5 +1,7 @@
 """An XBlock where students can read a question and compose their response"""
 
+from __future__ import absolute_import
+
 import copy
 import datetime as dt
 import json
@@ -9,6 +11,7 @@
 from lazy import lazy
 import pkg_resources
 import pytz
+from six import text_type
 from webob import Response
 from xblock.core import XBlock
 from xblock.fields import Boolean, Integer, List, Scope, String
@@ -362,7 +365,7 @@ def get_student_item_dict(self, anonymous_user_id=None):
             if self.scope_ids.user_id is None:
                 student_id = None
             else:
-                student_id = unicode(self.scope_ids.user_id)
+                student_id = text_type(self.scope_ids.user_id)
 
         student_item_dict = dict(
             student_id=student_id,
@@ -1104,7 +1107,7 @@ def _serialize_opaque_key(self, key):
         if hasattr(key, 'to_deprecated_string'):
             return key.to_deprecated_string()
         else:
-            return unicode(key)
+            return text_type(key)
 
     def get_username(self, anonymous_user_id):
         """
diff --git a/openassessment/xblock/resolve_dates.py b/openassessment/xblock/resolve_dates.py
index cbfb062ee2..f948cb57bb 100644
--- a/openassessment/xblock/resolve_dates.py
+++ b/openassessment/xblock/resolve_dates.py
@@ -1,10 +1,14 @@
 """
 Resolve unspecified dates and date strings to datetimes.
 """
+from __future__ import absolute_import
+
 import datetime as dt
 
 from dateutil.parser import parse as parse_date
 import pytz
+import six
+from six.moves import range, zip
 
 
 class InvalidDateFormat(Exception):
@@ -43,7 +47,7 @@ def _parse_date(value, _):
     if isinstance(value, dt.datetime):
         return value.replace(tzinfo=pytz.utc)
 
-    elif isinstance(value, basestring):
+    elif isinstance(value, six.string_types):
         try:
             return parse_date(value).replace(tzinfo=pytz.utc)
         except ValueError:
@@ -226,7 +230,7 @@ def resolve_dates(start, end, date_ranges, _):
         prev_end = step_end
 
     # Combine the resolved dates back into a list of tuples
-    resolved_ranges = zip(resolved_starts, resolved_ends)
+    resolved_ranges = list(zip(resolved_starts, resolved_ends))
 
     # Now that we have resolved both start and end dates, we can safely compare them
     for resolved_start, resolved_end in resolved_ranges:
diff --git a/openassessment/xblock/schema.py b/openassessment/xblock/schema.py
index 9cca820004..7f458d6cd7 100644
--- a/openassessment/xblock/schema.py
+++ b/openassessment/xblock/schema.py
@@ -2,8 +2,12 @@
 Schema for validating and sanitizing data received from the JavaScript client.
 """
 
+from __future__ import absolute_import
+
 import dateutil
 from pytz import utc
+import six
+
 from voluptuous import All, Any, In, Invalid, Range, Required, Schema
 
 
@@ -22,10 +26,10 @@ def utf8_validator(value):
 
     """
     try:
-        if isinstance(value, str):
+        if isinstance(value, six.binary_type):
             return value.decode('utf-8')
         else:
-            return unicode(value)
+            return six.text_type(value)
     except (ValueError, TypeError):
         raise Invalid(u"Could not load unicode from value \"{val}\"".format(val=value))
 
@@ -51,7 +55,7 @@ def datetime_validator(value):
 
         # Parse the date and interpret it as UTC
         value = dateutil.parser.parse(value).replace(tzinfo=utc)
-        return unicode(value.isoformat())
+        return six.text_type(value.isoformat())
     except (ValueError, TypeError):
         raise Invalid(u"Could not parse datetime from value \"{val}\"".format(val=value))
 
diff --git a/openassessment/xblock/staff_area_mixin.py b/openassessment/xblock/staff_area_mixin.py
index 429dd312ab..034fde6472 100644
--- a/openassessment/xblock/staff_area_mixin.py
+++ b/openassessment/xblock/staff_area_mixin.py
@@ -6,6 +6,7 @@
 from functools import wraps
 import logging
 
+import six
 from xblock.core import XBlock
 
 from openassessment.assessment.errors import PeerAssessmentInternalError
@@ -485,6 +486,6 @@ def _cancel_workflow(self, submission_uuid, comments, requesting_user_id=None):
                 AssessmentWorkflowError,
                 AssessmentWorkflowInternalError
         ) as ex:
-            msg = ex.message
+            msg = six.text_type(ex)
             logger.exception(msg)
             return {"success": False, 'msg': msg}
diff --git a/openassessment/xblock/staff_assessment_mixin.py b/openassessment/xblock/staff_assessment_mixin.py
index b102b517c0..d6bd537064 100644
--- a/openassessment/xblock/staff_assessment_mixin.py
+++ b/openassessment/xblock/staff_assessment_mixin.py
@@ -1,6 +1,9 @@
+# -*- coding: utf-8 -*-
 """""
 A mixin for staff grading.
 """
+from __future__ import absolute_import, division, print_function, unicode_literals
+
 import logging
 
 from xblock.core import XBlock
@@ -8,9 +11,9 @@
 from openassessment.assessment.api import staff as staff_api
 from openassessment.assessment.errors import StaffAssessmentInternalError, StaffAssessmentRequestError
 from openassessment.workflow import api as workflow_api
-from staff_area_mixin import require_course_staff
 
 from .data_conversion import clean_criterion_feedback, create_rubric_dict, verify_assessment_parameters
+from .staff_area_mixin import require_course_staff
 
 logger = logging.getLogger(__name__)
 
diff --git a/openassessment/xblock/student_training_mixin.py b/openassessment/xblock/student_training_mixin.py
index 012a1ad024..f198db2ad0 100644
--- a/openassessment/xblock/student_training_mixin.py
+++ b/openassessment/xblock/student_training_mixin.py
@@ -1,8 +1,12 @@
 """
 Student training step in the OpenAssessment XBlock.
 """
+from __future__ import absolute_import
+
 import logging
 
+import six
+
 from webob import Response
 from xblock.core import XBlock
 
@@ -64,14 +68,14 @@ def _parse_answer_dict(self, answer):
         """
         parts = answer.get('parts', [])
         if parts and isinstance(parts[0], dict):
-            if isinstance(parts[0].get('text'), basestring):
+            if isinstance(parts[0].get('text'), six.string_types):
                 return create_submission_dict({'answer': answer}, self.prompts)
 
     def _parse_answer_list(self, answer):
         """
         Helper to parse answer as a list of strings.
         """
-        if answer and isinstance(answer[0], basestring):
+        if answer and isinstance(answer[0], six.string_types):
             return self._parse_answer_string(answer[0])
         elif len(answer) == 0:
             return self._parse_answer_string("")
@@ -100,7 +104,7 @@ def _parse_example(self, example):
             )
         answer = example['answer']
         submission_dict = None
-        if isinstance(answer, basestring):
+        if isinstance(answer, six.string_types):
             submission_dict = self._parse_answer_string(answer)
         elif isinstance(answer, dict):
             submission_dict = self._parse_answer_dict(answer)
diff --git a/openassessment/xblock/studio_mixin.py b/openassessment/xblock/studio_mixin.py
index 264a95eb8e..4131ef5bfc 100644
--- a/openassessment/xblock/studio_mixin.py
+++ b/openassessment/xblock/studio_mixin.py
@@ -1,11 +1,15 @@
 """
 Studio editing view for OpenAssessment XBlock.
 """
+from __future__ import absolute_import
+
 import copy
 import logging
 from uuid import uuid4
 
 import pkg_resources
+import six
+from six.moves import range, zip
 from voluptuous import MultipleInvalid
 from xblock.core import XBlock
 from xblock.fields import List, Scope
@@ -384,7 +388,7 @@ def _get_base_url_path_for_course_assets(self, course_key):
 
         placeholder_id = uuid4().hex
         # create a dummy asset location with a fake but unique name. strip off the name, and return it
-        url_path = unicode(course_key.make_asset_key('asset', placeholder_id).for_branch(None))
+        url_path = six.text_type(course_key.make_asset_key('asset', placeholder_id).for_branch(None))
         if not url_path.startswith('/'):
             url_path = '/' + url_path
         return url_path.replace(placeholder_id, '')
diff --git a/openassessment/xblock/submission_mixin.py b/openassessment/xblock/submission_mixin.py
index 07b4fc4b4c..421bd80a51 100644
--- a/openassessment/xblock/submission_mixin.py
+++ b/openassessment/xblock/submission_mixin.py
@@ -1,16 +1,20 @@
+# -*- coding: utf-8 -*-
+from __future__ import absolute_import, division, print_function, unicode_literals
+
 import json
 import logging
 
+import six
 from xblock.core import XBlock
 
-from data_conversion import create_submission_dict, prepare_submission_for_serialization
 from openassessment.fileupload import api as file_upload_api
 from openassessment.fileupload.exceptions import FileUploadError
 from openassessment.workflow.errors import AssessmentWorkflowError
-from validation import validate_submission
 
+from .data_conversion import create_submission_dict, prepare_submission_for_serialization
 from .resolve_dates import DISTANT_FUTURE
 from .user_data import get_user_preferences
+from .validation import validate_submission
 
 logger = logging.getLogger(__name__)
 
@@ -208,7 +212,10 @@ def save_files_descriptions(self, data, suffix=''):  # pylint: disable=unused-ar
         if 'descriptions' in data:
             descriptions = data['descriptions']
 
-            if isinstance(descriptions, list) and all(map(lambda description: isinstance(description, basestring), descriptions)):
+            if (
+                    isinstance(descriptions, list) and
+                    all(isinstance(description, six.string_types) for description in descriptions)
+            ):
                 try:
                     self.saved_files_descriptions = json.dumps(descriptions)
 
diff --git a/openassessment/xblock/test/base.py b/openassessment/xblock/test/base.py
index 78e5e91e1a..0abbe225c4 100644
--- a/openassessment/xblock/test/base.py
+++ b/openassessment/xblock/test/base.py
@@ -2,12 +2,15 @@
 """
 Base class for handler-level testing of the XBlock.
 """
+from __future__ import absolute_import, print_function
+
 import copy
 from functools import wraps
 import json
 import os.path
 
 import mock
+from six.moves import zip
 import webob
 from workbench.runtime import WorkbenchRuntime
 
@@ -102,7 +105,7 @@ def _wrapped(*args, **kwargs):
                 if isinstance(self, XBlockHandlerTestCaseMixin):
 
                     # Print a debug message
-                    print "Loading scenario from {path}".format(path=scenario_path)
+                    print("Loading scenario from {path}".format(path=scenario_path))
 
                     # Configure the runtime with our user id
                     self.set_user(user_id)
@@ -185,7 +188,7 @@ def request(self, xblock, handler_name, content, request_method="POST", response
         # Create a fake request
         request = webob.Request(dict())
         request.method = request_method
-        request.body = content
+        request.body = content.encode('utf-8')
 
         # Send the request to the XBlock handler
         if use_runtime:
diff --git a/openassessment/xblock/test/test_grade.py b/openassessment/xblock/test/test_grade.py
index 06fc3769f6..bcda608d52 100644
--- a/openassessment/xblock/test/test_grade.py
+++ b/openassessment/xblock/test/test_grade.py
@@ -6,6 +6,7 @@
 import json
 
 import ddt
+import six
 
 from openassessment.assessment.api import peer as peer_api
 
@@ -37,18 +38,18 @@ def test_render_grade(self, xblock):
         # This isn't strictly speaking part of the grade step rendering,
         # but we've already done all the setup to get to this point in the flow,
         # so we might as well verify it here.
-        resp = self.request(xblock, 'render_submission', json.dumps(dict()))
+        resp = self.request(xblock, 'render_submission', json.dumps(dict())).decode('utf-8')
         self.assertIn('response', resp.lower())
         self.assertIn('complete', resp.lower())
 
         # Verify that student submission is in the view
-        self.assertIn(self.SUBMISSION[1], resp.decode('utf-8'))
+        self.assertIn(self.SUBMISSION[1], resp)
 
-        resp = self.request(xblock, 'render_peer_assessment', json.dumps(dict()))
+        resp = self.request(xblock, 'render_peer_assessment', json.dumps(dict())).decode('utf-8')
         self.assertIn('peer', resp.lower())
         self.assertIn('complete', resp.lower())
 
-        resp = self.request(xblock, 'render_self_assessment', json.dumps(dict()))
+        resp = self.request(xblock, 'render_self_assessment', json.dumps(dict())).decode('utf-8')
         self.assertIn('self', resp.lower())
         self.assertIn('complete', resp.lower())
 
@@ -69,15 +70,15 @@ def test_render_grade_self_only(self, xblock):
         # This isn't strictly speaking part of the grade step rendering,
         # but we've already done all the setup to get to this point in the flow,
         # so we might as well verify it here.
-        resp = self.request(xblock, 'render_submission', json.dumps(dict()))
+        resp = self.request(xblock, 'render_submission', json.dumps(dict())).decode('utf-8')
         self.assertIn('response', resp.lower())
         self.assertIn('complete', resp.lower())
 
-        resp = self.request(xblock, 'render_peer_assessment', json.dumps(dict()))
+        resp = self.request(xblock, 'render_peer_assessment', json.dumps(dict())).decode('utf-8')
         self.assertNotIn('peer', resp.lower())
         self.assertNotIn('complete', resp.lower())
 
-        resp = self.request(xblock, 'render_self_assessment', json.dumps(dict()))
+        resp = self.request(xblock, 'render_self_assessment', json.dumps(dict())).decode('utf-8')
         self.assertIn('self', resp.lower())
         self.assertIn('complete', resp.lower())
 
@@ -103,12 +104,12 @@ def test_render_grade_feedback_only_criterion(self, xblock):
         )
 
         # Render the grade section
-        resp = self.request(xblock, 'render_grade', json.dumps(dict()))
+        resp = self.request(xblock, 'render_grade', json.dumps(dict())).decode('utf-8')
         self.assertIn('your response', resp.lower())
 
         # Verify that feedback from each scorer appears in the view
-        self.assertIn(u'єאςєɭɭєภՇ ฬ๏гк!', resp.decode('utf-8'))
-        self.assertIn(u'Good job!', resp.decode('utf-8'))
+        self.assertIn(u'єאςєɭɭєภՇ ฬ๏гк!', resp)
+        self.assertIn(u'Good job!', resp)
 
     @scenario('data/feedback_per_criterion.xml', user_id='Bernard')
     def test_render_grade_feedback(self, xblock):
@@ -251,7 +252,7 @@ def test_peer_update_after_override(self, xblock):
 
         # Create all but the last peer assessment of the current user; no peer grade will be available
         graded_by = xblock.get_assessment_module('peer-assessment')['must_be_graded_by']
-        for scorer_sub, scorer_name, assessment in zip(scorer_subs, self.PEERS, PEER_ASSESSMENTS)[:-1]:
+        for scorer_sub, scorer_name, assessment in list(zip(scorer_subs, self.PEERS, PEER_ASSESSMENTS))[:-1]:
             self.create_peer_assessment(
                 scorer_sub,
                 scorer_name,
@@ -336,7 +337,7 @@ def test_assessment_does_not_match_rubric(self, xblock):
         # (since it's not part of the original assessment),
         # but at least it won't display an error.
         resp = self.request(xblock, 'render_grade', json.dumps({}))
-        self.assertGreater(resp, 0)
+        self.assertGreater(len(resp), 0)
 
     @ddt.file_data('data/waiting_scenarios.json')
     @scenario('data/grade_waiting_scenario.xml', user_id='Omar')
@@ -405,7 +406,8 @@ def test_submit_feedback(self, xblock):
         feedback = peer_api.get_assessment_feedback(xblock.submission_uuid)
         self.assertIsNot(feedback, None)
         self.assertEqual(feedback['feedback_text'], u'I disliked my assessment')
-        self.assertItemsEqual(
+        six.assertCountEqual(
+            self,
             feedback['options'], [{'text': u'Option 1'}, {'text': u'Option 2'}]
         )
 
@@ -427,7 +429,7 @@ def test_submit_feedback_no_options(self, xblock):
         # Verify that the feedback was created in the database
         feedback = peer_api.get_assessment_feedback(xblock.submission_uuid)
         self.assertIsNot(feedback, None)
-        self.assertItemsEqual(feedback['options'], [])
+        six.assertCountEqual(self, feedback['options'], [])
 
     @scenario('data/grade_scenario.xml', user_id='Bob')
     def test_submit_feedback_invalid_options(self, xblock):
diff --git a/openassessment/xblock/test/test_staff.py b/openassessment/xblock/test/test_staff.py
index 2606b2dabf..8f02e8b159 100644
--- a/openassessment/xblock/test/test_staff.py
+++ b/openassessment/xblock/test/test_staff.py
@@ -6,6 +6,7 @@
 import json
 
 import mock
+import six
 
 from openassessment.assessment.api import staff as staff_api
 
@@ -20,7 +21,7 @@ def _assert_path_and_context(self, xblock, expected_context):
         path, context = xblock.staff_path_and_context()
 
         self.assertEqual('openassessmentblock/staff/oa_staff_grade.html', path)
-        self.assertItemsEqual(expected_context, context)
+        six.assertCountEqual(self, expected_context, context)
 
         # Verify that we render without error
         resp = self.request(xblock, 'render_staff_assessment', json.dumps({}))
@@ -161,7 +162,7 @@ def test_staff_assess_handler(self, xblock):
         self.assertEqual(assessment['score_type'], 'ST')
         self.assertEqual(assessment['feedback'], u'Staff: good job!')
 
-        parts = sorted(assessment['parts'])
+        parts = sorted(assessment['parts'], key=lambda part: part['option']['name'])
         self.assertEqual(len(parts), 2)
         self.assertEqual(parts[0]['option']['criterion']['name'], u'Form')
         self.assertEqual(parts[0]['option']['name'], 'Fair')
@@ -201,7 +202,7 @@ def test_permission_error(self, xblock):
         student_item = xblock.get_student_item_dict()
         xblock.create_submission(student_item, self.SUBMISSION)
         resp = self.request(xblock, 'staff_assess', json.dumps(STAFF_GOOD_ASSESSMENT))
-        self.assertIn("You do not have permission", resp)
+        self.assertIn("You do not have permission", resp.decode('utf-8'))
 
     @scenario('data/self_assessment_scenario.xml', user_id='Bob')
     def test_invalid_options(self, xblock):
diff --git a/openassessment/xblock/test/test_staff_area.py b/openassessment/xblock/test/test_staff_area.py
index 0907d3a628..eaa9bd687c 100644
--- a/openassessment/xblock/test/test_staff_area.py
+++ b/openassessment/xblock/test/test_staff_area.py
@@ -4,9 +4,9 @@
 """
 from collections import namedtuple
 import json
-import urllib
 
 from mock import MagicMock, Mock, call, patch
+from six.moves.urllib.parse import urlencode
 
 from openassessment.assessment.api import peer as peer_api
 from openassessment.assessment.api import self as self_api
@@ -169,7 +169,7 @@ def test_staff_area_student_info_no_submission(self, xblock):
         request.params = {"student_id": "test_student"}
         # Verify that we can render without error
         resp = xblock.render_student_info(request)
-        self.assertIn("a response was not found for this learner.", resp.body.lower())
+        self.assertIn("a response was not found for this learner.", resp.body.decode('utf-8').lower())
 
     @scenario('data/peer_only_scenario.xml', user_id='Bob')
     def test_staff_area_student_info_peer_only(self, xblock):
@@ -277,8 +277,8 @@ def test_staff_area_student_info_staff_only_no_options(self, xblock):
             self.request(
                 xblock,
                 "render_student_info",
-                urllib.urlencode({"student_username": "Bob"})
-            )
+                urlencode({"student_username": "Bob"})
+            ).decode('utf-8')
         )
 
     @scenario('data/staff_grade_scenario.xml', user_id='Bob')
@@ -415,8 +415,8 @@ def test_staff_area_student_info_image_submission(self, xblock):
             self.assertEquals('image', context['file_upload_type'])
 
             # Check the fully rendered template
-            payload = urllib.urlencode({"student_username": "Bob"})
-            resp = self.request(xblock, "render_student_info", payload)
+            payload = urlencode({"student_username": "Bob"})
+            resp = self.request(xblock, "render_student_info", payload).decode('utf-8')
             self.assertIn("http://www.example.com/image.jpeg", resp)
 
     @scenario('data/self_only_scenario.xml', user_id='Bob')
@@ -465,8 +465,8 @@ def test_staff_area_student_info_many_images_submission(self, xblock):
             self.assertEquals('image', context['file_upload_type'])
 
             # Check the fully rendered template
-            payload = urllib.urlencode({"student_username": "Bob"})
-            resp = self.request(xblock, "render_student_info", payload)
+            payload = urlencode({"student_username": "Bob"})
+            resp = self.request(xblock, "render_student_info", payload).decode('utf-8')
             for i in range(3):
                 self.assertIn("http://www.example.com/image%d.jpeg" % i, resp)
                 self.assertIn("test_description%d" % i, resp)
@@ -498,8 +498,8 @@ def test_staff_area_student_info_file_download_url_error(self, xblock):
             self.assertNotIn('file_url', context['submission'])
 
             # Check the fully rendered template
-            payload = urllib.urlencode({"student_username": "Bob"})
-            resp = self.request(xblock, "render_student_info", payload)
+            payload = urlencode({"student_username": "Bob"})
+            resp = self.request(xblock, "render_student_info", payload).decode('utf-8')
             self.assertIn("Bob Answer", resp)
 
     @scenario('data/grade_scenario.xml', user_id='Bob')
@@ -559,7 +559,7 @@ def test_staff_area_student_info_full_workflow(self, xblock):
         request.params = {"student_username": "Bob"}
         # Verify that we can render without error
         resp = xblock.render_student_info(request)
-        self.assertIn("bob answer", resp.body.lower())
+        self.assertIn("bob answer", resp.body.decode('utf-8').lower())
 
     @scenario('data/basic_scenario.xml', user_id='Bob')
     def test_cancel_submission_without_reason(self, xblock):
@@ -711,14 +711,14 @@ def test_staff_delete_student_state(self, xblock):
         request.params = {"student_username": 'Bob'}
         # Verify that we can see the student's grade
         resp = xblock.render_student_info(request)
-        self.assertIn("final grade", resp.body.lower())
+        self.assertIn("final grade", resp.body.decode('utf-8').lower())
 
         # Staff user Bob can clear his own submission
         xblock.clear_student_state('Bob', 'test_course', xblock.scope_ids.usage_id, bob_item['student_id'])
 
         # Verify that the submission was cleared
         resp = xblock.render_student_info(request)
-        self.assertIn("response was not found", resp.body.lower())
+        self.assertIn("response was not found", resp.body.decode('utf-8').lower())
 
     def _verify_staff_assessment_context(self, context, required, ungraded=None, in_progress=None):
         """
diff --git a/openassessment/xblock/test/test_submission.py b/openassessment/xblock/test/test_submission.py
index 62a8807817..ecea5a64ef 100644
--- a/openassessment/xblock/test/test_submission.py
+++ b/openassessment/xblock/test/test_submission.py
@@ -119,7 +119,7 @@ def test_ability_to_submit_blank_answer_if_text_response_none(self, xblock):
     @scenario('data/over_grade_scenario.xml', user_id='Alice')
     def test_closed_submissions(self, xblock):
         resp = self.request(xblock, 'render_submission', json.dumps(dict()))
-        self.assertIn("Incomplete", resp)
+        self.assertIn("Incomplete", resp.decode('utf-8'))
 
     @scenario('data/line_breaks.xml')
     def test_prompt_line_breaks(self, xblock):
@@ -127,18 +127,18 @@ def test_prompt_line_breaks(self, xblock):
         # (backward compatibility in case if prompt_type == 'text')
         resp = self.request(xblock, 'render_submission', json.dumps(dict()))
         expected_prompt = u"<p><br />Line 1</p><p>Line 2</p><p>Line 3<br /></p>"
-        self.assertIn(expected_prompt, resp)
+        self.assertIn(expected_prompt, resp.decode('utf-8'))
 
     @scenario('data/prompt_html.xml')
     def test_prompt_html_to_text(self, xblock):
         resp = self.request(xblock, 'render_submission', json.dumps(dict()))
         expected_prompt = u"<code><strong>Question 123</strong></code>"
-        self.assertIn(expected_prompt, resp)
+        self.assertIn(expected_prompt, resp.decode('utf-8'))
 
         xblock.prompts_type = "text"
         resp = self.request(xblock, 'render_submission', json.dumps(dict()))
         expected_prompt = "&lt;code&gt;&lt;strong&gt;Question 123&lt;/strong&gt;&lt;/code&gt;"
-        self.assertIn(expected_prompt, resp)
+        self.assertIn(expected_prompt, resp.decode('utf-8'))
 
     @mock_s3
     @override_settings(
@@ -156,10 +156,10 @@ def test_upload_url(self, xblock):
         resp = self.request(xblock, 'upload_url', json.dumps({"contentType": "image/jpeg",
                                                               "filename": "test.jpg"}), response_format='json')
         self.assertTrue(resp['success'])
-        self.assertTrue(resp['url'].startswith(
-            'https://mybucket.s3.amazonaws.com/submissions_attachments/test_student/test_course/' +
-            xblock.scope_ids.usage_id
-        ))
+        self.assertIn(
+            '/submissions_attachments/test_student/test_course/' + xblock.scope_ids.usage_id,
+            resp['url']
+        )
 
     @mock_s3
     @override_settings(
@@ -251,10 +251,10 @@ def test_upload_files_with_uppercase_ext(self, xblock):
         resp = self.request(xblock, 'upload_url', json.dumps({'contentType': 'filename',
                                                               'filename': 'test.PDF'}), response_format='json')
         self.assertTrue(resp['success'])
-        self.assertTrue(resp['url'].startswith(
-            'https://mybucket.s3.amazonaws.com/submissions_attachments/test_student/test_course/' +
-            xblock.scope_ids.usage_id
-        ))
+        self.assertIn(
+            '/submissions_attachments/test_student/test_course/' + xblock.scope_ids.usage_id,
+            resp['url']
+        )
 
 
 class SubmissionRenderTest(XBlockHandlerTestCase):
@@ -601,8 +601,8 @@ def test_closed_graded(self, xblock):
     def test_integration(self, xblock):
         # Expect that the response step is open and displays the deadline
         resp = self.request(xblock, 'render_submission', json.dumps(dict()))
-        self.assertIn('Enter your response to the prompt', resp)
-        self.assertIn('2999-05-06T00:00:00+00:00', resp)
+        self.assertIn('Enter your response to the prompt', resp.decode('utf-8'))
+        self.assertIn('2999-05-06T00:00:00+00:00', resp.decode('utf-8'))
 
         # Create a submission for the user
         xblock.create_submission(
@@ -612,7 +612,7 @@ def test_integration(self, xblock):
 
         # Expect that the response step is "submitted"
         resp = self.request(xblock, 'render_submission', json.dumps(dict()))
-        self.assertIn('your response has been submitted', resp.lower())
+        self.assertIn('your response has been submitted', resp.decode('utf-8').lower())
 
     def _assert_path_and_context(self, xblock, expected_path, expected_context):
         """
diff --git a/openassessment/xblock/validation.py b/openassessment/xblock/validation.py
index 12d7de62a6..41a5b0006a 100644
--- a/openassessment/xblock/validation.py
+++ b/openassessment/xblock/validation.py
@@ -1,8 +1,13 @@
 """
 Validate changes to an XBlock before it is updated.
 """
+from __future__ import absolute_import
+
 from collections import Counter
 
+import six
+from six.moves import zip
+
 from openassessment.assessment.api.student_training import validate_training_examples
 from openassessment.assessment.serializers import InvalidRubric, rubric_from_dict
 from openassessment.xblock.data_conversion import convert_training_examples_list_to_dict
@@ -27,7 +32,7 @@ def _match_by_order(items, others):
     """
     # Sort each dictionary by its "name" key, then zip them and return
     key_func = lambda x: x['order_num']
-    return zip(sorted(items, key=key_func), sorted(others, key=key_func))
+    return list(zip(sorted(items, key=key_func), sorted(others, key=key_func)))
 
 
 def _duplicates(items):
@@ -258,7 +263,7 @@ def validate_dates(start, end, date_ranges, _):
     try:
         resolve_dates(start, end, date_ranges, _)
     except (DateValidationError, InvalidDateFormat) as ex:
-        return False, unicode(ex)
+        return False, six.text_type(ex)
     else:
         return True, u''
 
@@ -382,7 +387,7 @@ def validate_submission(submission, prompts, _, text_response='required'):
         return False, message
 
     for submission_part in submission:
-        if type(submission_part) != unicode:
+        if type(submission_part) != six.text_type:
             return False, message
 
     return True, u''
diff --git a/openassessment/xblock/xml.py b/openassessment/xblock/xml.py
index 899bea8c04..22270c9615 100644
--- a/openassessment/xblock/xml.py
+++ b/openassessment/xblock/xml.py
@@ -1,6 +1,8 @@
 """
 Serialize and deserialize OpenAssessment XBlock content to/from XML.
 """
+from __future__ import absolute_import
+
 from uuid import uuid4 as uuid
 import logging
 import json
@@ -9,6 +11,7 @@
 import defusedxml.ElementTree as safe_etree
 import lxml.etree as etree
 import pytz
+import six
 
 from openassessment.xblock.data_conversion import update_assessments_format
 from openassessment.xblock.lms_mixin import GroupAccessDict
@@ -59,7 +62,7 @@ def _safe_get_text(element):
     Returns:
         unicode
     """
-    return unicode(element.text) if element.text is not None else u""
+    return six.text_type(element.text) if element.text is not None else u""
 
 
 def _serialize_prompts(prompts_root, prompts_list):
@@ -82,7 +85,7 @@ def _serialize_prompts(prompts_root, prompts_list):
 
         # Prompt description
         prompt_description = etree.SubElement(prompt_el, 'description')
-        prompt_description.text = unicode(prompt.get('description', u''))
+        prompt_description.text = six.text_type(prompt.get('description', u''))
 
 
 def _serialize_options(options_root, options_list):
@@ -105,22 +108,22 @@ def _serialize_options(options_root, options_list):
         option_el = etree.SubElement(options_root, 'option')
 
         # Points (default to 0)
-        option_el.set('points', unicode(option.get('points', 0)))
+        option_el.set('points', six.text_type(option.get('points', 0)))
 
         # Name (default to a UUID)
         option_name = etree.SubElement(option_el, 'name')
         if 'name' in option:
-            option_name.text = unicode(option['name'])
+            option_name.text = six.text_type(option['name'])
         else:
-            option_name.text = unicode(uuid().hex)
+            option_name.text = six.text_type(uuid().hex)
 
         # Label (default to the option name, then an empty string)
         option_label = etree.SubElement(option_el, 'label')
-        option_label.text = unicode(option.get('label', option.get('name', u'')))
+        option_label.text = six.text_type(option.get('label', option.get('name', u'')))
 
         # Explanation (default to empty str)
         option_explanation = etree.SubElement(option_el, 'explanation')
-        option_explanation.text = unicode(option.get('explanation', u''))
+        option_explanation.text = six.text_type(option.get('explanation', u''))
 
 
 def _serialize_criteria(criteria_root, criteria_list):
@@ -146,17 +149,17 @@ def _serialize_criteria(criteria_root, criteria_list):
         # Criterion name (default to a UUID)
         criterion_name = etree.SubElement(criterion_el, u'name')
         if 'name' in criterion:
-            criterion_name.text = unicode(criterion['name'])
+            criterion_name.text = six.text_type(criterion['name'])
         else:
-            criterion_name.text = unicode(uuid().hex)
+            criterion_name.text = six.text_type(uuid().hex)
 
         # Criterion label (default to the name, then an empty string)
         criterion_label = etree.SubElement(criterion_el, 'label')
-        criterion_label.text = unicode(criterion.get('label', criterion.get('name', u'')))
+        criterion_label.text = six.text_type(criterion.get('label', criterion.get('name', u'')))
 
         # Criterion prompt (default to empty string)
         criterion_prompt = etree.SubElement(criterion_el, 'prompt')
-        criterion_prompt.text = unicode(criterion.get('prompt', u''))
+        criterion_prompt.text = six.text_type(criterion.get('prompt', u''))
 
         # Criterion feedback disabled, optional, or required
         # If disabled, do not set the attribute.
@@ -194,11 +197,11 @@ def serialize_rubric(rubric_root, oa_block):
 
     if oa_block.rubric_feedback_prompt is not None:
         feedback_prompt = etree.SubElement(rubric_root, 'feedbackprompt')
-        feedback_prompt.text = unicode(oa_block.rubric_feedback_prompt)
+        feedback_prompt.text = six.text_type(oa_block.rubric_feedback_prompt)
 
     if oa_block.rubric_feedback_default_text is not None:
         feedback_text = etree.SubElement(rubric_root, 'feedback_default_text')
-        feedback_text.text = unicode(oa_block.rubric_feedback_default_text)
+        feedback_text.text = six.text_type(oa_block.rubric_feedback_default_text)
 
 
 def parse_date(date_str, name=""):
@@ -223,9 +226,9 @@ def parse_date(date_str, name=""):
         return None
     try:
         # Get the date into ISO format
-        parsed_date = dateutil.parser.parse(unicode(date_str)).replace(tzinfo=pytz.utc)
+        parsed_date = dateutil.parser.parse(six.text_type(date_str)).replace(tzinfo=pytz.utc)
         formatted_date = parsed_date.strftime("%Y-%m-%dT%H:%M:%S")
-        return unicode(formatted_date)
+        return six.text_type(formatted_date)
     except (ValueError, TypeError):
         msg = (
             'The format of the given date ({date}) for the {name} is invalid. '
@@ -499,8 +502,8 @@ def parse_examples_xml(examples):
                 raise UpdateFromXmlError(u'Each "select" element must have an "option" attribute')
 
             example_dict['options_selected'].append({
-                'criterion': unicode(select_el.get('criterion')),
-                'option': unicode(select_el.get('option'))
+                'criterion': six.text_type(select_el.get('criterion')),
+                'option': six.text_type(select_el.get('option'))
             })
 
         examples_list.append(example_dict)
@@ -530,7 +533,7 @@ def parse_assessments_xml(assessments_root):
 
         # Assessment name
         if 'name' in assessment.attrib:
-            assessment_dict['name'] = unicode(assessment.get('name'))
+            assessment_dict['name'] = six.text_type(assessment.get('name'))
         else:
             raise UpdateFromXmlError('All "assessment" elements must contain a "name" element.')
 
@@ -576,7 +579,7 @@ def parse_assessments_xml(assessments_root):
             # Staff assessment is the only type to use an explicit required marker
             if assessment_dict['name'] != 'staff-assessment':
                 raise UpdateFromXmlError('The "required" field is only allowed for staff assessment.')
-            assessment_dict['required'] = _parse_boolean(unicode(assessment.get('required')))
+            assessment_dict['required'] = _parse_boolean(six.text_type(assessment.get('required')))
 
         # Training examples
         examples = assessment.findall('example')
@@ -622,7 +625,7 @@ def serialize_training_examples(examples, assessment_el):
 
             for part in parts:
                 part_el = etree.SubElement(answer_el, 'part')
-                part_el.text = unicode(part.get('text', u''))
+                part_el.text = six.text_type(part.get('text', u''))
         except: # excuse the bare-except, looking for more information on EDUCATOR-1817
             log.exception('Error parsing training example: %s', example_dict)
             raise
@@ -631,8 +634,8 @@ def serialize_training_examples(examples, assessment_el):
         options_selected = example_dict.get('options_selected', [])
         for selected_dict in options_selected:
             select_el = etree.SubElement(example_el, 'select')
-            select_el.set('criterion', unicode(selected_dict.get('criterion', '')))
-            select_el.set('option', unicode(selected_dict.get('option', '')))
+            select_el.set('criterion', six.text_type(selected_dict.get('criterion', '')))
+            select_el.set('option', six.text_type(selected_dict.get('option', '')))
 
 
 def serialize_assessments(assessments_root, oa_block):
@@ -653,22 +656,22 @@ def serialize_assessments(assessments_root, oa_block):
         assessment = etree.SubElement(assessments_root, 'assessment')
 
         # Set assessment attributes, defaulting to empty values
-        assessment.set('name', unicode(assessment_dict.get('name', '')))
+        assessment.set('name', six.text_type(assessment_dict.get('name', '')))
 
         if 'must_grade' in assessment_dict:
-            assessment.set('must_grade', unicode(assessment_dict['must_grade']))
+            assessment.set('must_grade', six.text_type(assessment_dict['must_grade']))
 
         if 'must_be_graded_by' in assessment_dict:
-            assessment.set('must_be_graded_by', unicode(assessment_dict['must_be_graded_by']))
+            assessment.set('must_be_graded_by', six.text_type(assessment_dict['must_be_graded_by']))
 
         if assessment_dict.get('start') is not None:
-            assessment.set('start', unicode(assessment_dict['start']))
+            assessment.set('start', six.text_type(assessment_dict['start']))
 
         if assessment_dict.get('due') is not None:
-            assessment.set('due', unicode(assessment_dict['due']))
+            assessment.set('due', six.text_type(assessment_dict['due']))
 
         if assessment_dict.get('required') is not None:
-            assessment.set('required', unicode(assessment_dict['required']))
+            assessment.set('required', six.text_type(assessment_dict['required']))
 
         # Training examples
         examples = assessment_dict.get('examples', [])
@@ -693,34 +696,34 @@ def serialize_content_to_xml(oa_block, root):
 
     # Set the submission start date
     if oa_block.submission_start is not None:
-        root.set('submission_start', unicode(oa_block.submission_start))
+        root.set('submission_start', six.text_type(oa_block.submission_start))
 
     # Set submission due date
     if oa_block.submission_due is not None:
-        root.set('submission_due', unicode(oa_block.submission_due))
+        root.set('submission_due', six.text_type(oa_block.submission_due))
 
     # Set leaderboard show
     if oa_block.leaderboard_show:
-        root.set('leaderboard_show', unicode(oa_block.leaderboard_show))
+        root.set('leaderboard_show', six.text_type(oa_block.leaderboard_show))
 
     # Set text response
     if oa_block.text_response:
-        root.set('text_response', unicode(oa_block.text_response))
+        root.set('text_response', six.text_type(oa_block.text_response))
 
     # Set file upload response
     if oa_block.file_upload_response:
-        root.set('file_upload_response', unicode(oa_block.file_upload_response))
+        root.set('file_upload_response', six.text_type(oa_block.file_upload_response))
 
     # Set File upload settings
     if oa_block.file_upload_type:
-        root.set('file_upload_type', unicode(oa_block.file_upload_type))
+        root.set('file_upload_type', six.text_type(oa_block.file_upload_type))
 
     # Set File type white listing
     if oa_block.white_listed_file_types:
-        root.set('white_listed_file_types', unicode(oa_block.white_listed_file_types_string))
+        root.set('white_listed_file_types', six.text_type(oa_block.white_listed_file_types_string))
 
     if oa_block.allow_latex is not None:
-        root.set('allow_latex', unicode(oa_block.allow_latex))
+        root.set('allow_latex', six.text_type(oa_block.allow_latex))
 
     # Set group access setting if not empty
     if oa_block.group_access:
@@ -728,7 +731,7 @@ def serialize_content_to_xml(oa_block, root):
 
     # Open assessment displayed title
     title = etree.SubElement(root, 'title')
-    title.text = unicode(oa_block.title)
+    title.text = six.text_type(oa_block.title)
 
     # Assessment list
     assessments_root = etree.SubElement(root, 'assessments')
@@ -738,7 +741,7 @@ def serialize_content_to_xml(oa_block, root):
     prompts_root = etree.SubElement(root, 'prompts')
     _serialize_prompts(prompts_root, oa_block.prompts)
 
-    root.set('prompts_type', unicode(oa_block.prompts_type))
+    root.set('prompts_type', six.text_type(oa_block.prompts_type))
 
     # Rubric
     rubric_root = etree.SubElement(root, 'rubric')
@@ -842,37 +845,37 @@ def parse_from_xml(root):
     # Set it to None by default; we will update it to the latest start date later on
     submission_start = None
     if 'submission_start' in root.attrib:
-        submission_start = parse_date(unicode(root.attrib['submission_start']), name="submission start date")
+        submission_start = parse_date(six.text_type(root.attrib['submission_start']), name="submission start date")
 
     # Retrieve the due date for the submission
     # Set it to None by default; we will update it to the earliest deadline later on
     submission_due = None
     if 'submission_due' in root.attrib:
-        submission_due = parse_date(unicode(root.attrib['submission_due']), name="submission due date")
+        submission_due = parse_date(six.text_type(root.attrib['submission_due']), name="submission due date")
 
     text_response = None
     if 'text_response' in root.attrib:
-        text_response = unicode(root.attrib['text_response'])
+        text_response = six.text_type(root.attrib['text_response'])
 
     file_upload_response = None
     if 'file_upload_response' in root.attrib:
-        file_upload_response = unicode(root.attrib['file_upload_response'])
+        file_upload_response = six.text_type(root.attrib['file_upload_response'])
 
     allow_file_upload = None
     if 'allow_file_upload' in root.attrib:
-        allow_file_upload = _parse_boolean(unicode(root.attrib['allow_file_upload']))
+        allow_file_upload = _parse_boolean(six.text_type(root.attrib['allow_file_upload']))
 
     file_upload_type = None
     if 'file_upload_type' in root.attrib:
-        file_upload_type = unicode(root.attrib['file_upload_type'])
+        file_upload_type = six.text_type(root.attrib['file_upload_type'])
 
     white_listed_file_types = None
     if 'white_listed_file_types' in root.attrib:
-        white_listed_file_types = unicode(root.attrib['white_listed_file_types'])
+        white_listed_file_types = six.text_type(root.attrib['white_listed_file_types'])
 
     allow_latex = False
     if 'allow_latex' in root.attrib:
-        allow_latex = _parse_boolean(unicode(root.attrib['allow_latex']))
+        allow_latex = _parse_boolean(six.text_type(root.attrib['allow_latex']))
 
     group_access = {}
     if 'group_access' in root.attrib:
@@ -897,7 +900,7 @@ def parse_from_xml(root):
 
     prompts_type = 'text'
     if 'prompts_type' in root.attrib:
-        prompts_type = unicode(root.attrib['prompts_type'])
+        prompts_type = six.text_type(root.attrib['prompts_type'])
 
     # Retrieve the leaderboard if it exists, otherwise set it to 0
     leaderboard_show = 0