BUILD_ENV_INPUT: rootpath instead of location

[matoubidou]

Thanks for this easy-to-use bazel rules for creating python virtual envs. When I was trying to use your rules from rules_multirun, i.e.

py_venv(
    name = "venv",
    venv_location = "venv",
    deps = all_requirements,
)

multirun(
    name = "install",
    commands = [
        ":venv",
        ...
    ],
)

, I ran into

Running @//devtools:venv
Traceback (most recent call last):
  File "/home/mgoeppe/.cache/bazel/_bazel_mgoeppe/f2e51ebbf887ec6078fbe8751b948440/execroot/ci/bazel-out/k8-fastbuild/bin/devtools/install.bash.runfiles/rules_pyvenv/build_env.py", line 278, in <module>
    main()
  File "/home/mgoeppe/.cache/bazel/_bazel_mgoeppe/f2e51ebbf887ec6078fbe8751b948440/execroot/ci/bazel-out/k8-fastbuild/bin/devtools/install.bash.runfiles/rules_pyvenv/build_env.py", line 251, in main
    with open(os.environ["BUILD_ENV_INPUT"]) as f:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: 'bazel-out/k8-fastbuild/bin/devtools/_venv_deps.json'

. This is caused by the funny behavior of location, see make variable documentation for details. I now fixed things by using rootpath instead. When I get things right this fix won't work on windows or when doing cross-compilation builds - but I doubt that this is needed for a venv.

For me things are working using it wrapped by multienv as well as invoking it directly.

_{Mathias Zeller mathias.zeller@mercedes-benz.com Mercedes-Benz Tech Innovation GmbH (ProviderInformation)}