Use Python 3.6 and Cython 0.26 to install wikidata_linker_utils

[fengh16]

There are many problems when install wikidata_linker_utils with python3.7 or Cython > 0.26.

Issue about Cython >0.26:

• successor_mask.pyx:1052:34: ambiguous overloaded method #38

Problems using Python3.7:

• Python 3.7 introduced a change which made async a reserved keyword, but Cython < 0.27.2 has a statement await = None, which will cause an error SyntaxError: invalid syntax
• If you use Python3.7 together with Cython0.27.2, you will get many problems like this:

‘PyThreadState {aka struct _ts}’ has no member named ‘exc_type’; did you mean ‘curexc_type’

[ArashAmani]

Thank

There are many problems when install wikidata_linker_utils with python3.7 or Cython > 0.26.

Issue about Cython >0.26:

• successor_mask.pyx:1052:34: ambiguous overloaded method #38

Problems using Python3.7:

• Python 3.7 introduced a change which made async a reserved keyword, but Cython < 0.27.2 has a statement await = None, which will cause an error SyntaxError: invalid syntax
• If you use Python3.7 together with Cython0.27.2, you will get many problems like this:

‘PyThreadState {aka struct _ts}’ has no member named ‘exc_type’; did you mean ‘curexc_type’

thanks a lot. my problem has been solved.
I create a virtual env with python 3.6 then install Cython 0.26