django_file_prefixes() raises TypeError if Django is imported by namespace

[Jacob Walls]

cd one level above your django checkout, and launch a python shell.

Calling django_file_prefixes will fail:

>>> import django
>>> django.__file__ is None
True
>>> from django.utils.deprecation import django_file_prefixes
>>> django_file_prefixes()
Traceback (most recent call last):
  File "<python-input-1>", line 5, in <module>
    django_file_prefixes()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/Users/jwalls/django/django/utils/deprecation.py", line 18, in django_file_prefixes
    return (os.path.dirname(file),)
            ~~~~~~~~~~~~~~~^^^^^^
  File "<frozen posixpath>", line 178, in dirname
TypeError: expected str, bytes or os.PathLike object, not NoneType

---

How I found this was by testing deprecation warnings, so what I'm concluding is that deprecation warnings might crash in 6.0 if you import Django by namespace.

[Jacob Walls]

​PR

[Natalia Bidart]

Thank you Jacob! I find "cd one level above your django checkout, and launch a python shell" a bit of a niche use case but the fix is quite straightforward, so accepting.

[Jacob Walls]

Yeah, I only expect this to happen "accidentally" in CI/CD pipelines when cwd is not managed cleanly, similar to the issues we see crop up when django's runtests.py is sometimes run from /tests versus /.

[Jacob Walls <jacobtylerwalls@…>]

In c1d8646:

Fixed #36961 -- Fixed TypeError in deprecation warnings if Django is imported by namespace.

[Jacob Walls <jacobtylerwalls@…>]

In 1b22d53:

[6.0.x] Fixed #36961 -- Fixed TypeError in deprecation warnings if Django is imported by namespace.

Backport of c1d8646ec219b8b90ebdd463f40e5767876658a0 from main.