cython 0.29 produces invalid __path__, breaking nose

Cython 0.29 produces invalid __path__ module attributes, breaking nosetests (and possibly other tools).

According to the Python reference, “__path__ must be an iterable of strings, but it may be empty” (Python language reference, section 5.4.5).

• In cython 0.29, the __path__ attribute on a compiled module is None, which is not an iterable.
• In cython 0.28.5, there is no __path__ attribute on a compiled module.

Expected behaviour: Compiled modules have a valid __path__ attribute (or omit it altogether).

Impact on nosetests:

• When collecting tests to run, nose checks the __path__ attribute on each module; if it exists, nose attempts to iterate over it in order to find submodules to test. (If the attribute doesn’t exist, nose skips the iteration.)
• In cython 0.29, nose attempts to iterate the invalid __path__ attribute, giving a “‘NoneType’ object is not iterable” error.
• In cython 0.28.5, there is no __path__ attribute on a compiled module, so nose skips the iteration and proceeds without error; the new behaviour is therefore a regression as far as projects using nosetests are concerned.
• Error message given by nose when testing a module compiled by Cython 0.29:

    File ".../lib/python3.6/site-packages/nose/loader.py", line 343, in loadTestsFromModule
      for module_path in module_paths:
  TypeError: 'NoneType' object is not iterable
  

[hmaarrfk]

Yeah, but i would like to hear something from a Cython developer. They will probably want a test to ensure it doesn’t keep breaking things in the future.

[scoder]

Hopefully fixed in 792263575b900eafd99ee0bbfbff1f14fcd70cc3.