Failing test for black formatter missing install simulation

[Roelzkie]

The test on test.user_commands.tests.UtilsTests.test_run_formatters_handles_oserror_for_black_path attempts to assert a ​`FileNotFoundError` when simulating a missing black formatter installation.

./runtests.py user_commands.tests.UtilsTests.test_run_formatters_handles_oserror_for_black_path

However, it fails on the darwin platform, at least on MacOS v14.7.2 (Sonoma) M1 machine. I tested on a Linux platform, and the test passed.

The root issue is due to the subprocess.run command, which yields different OSError results on different OS's when the test reaches the ​`subprocess.run(["nonexistent", "--fast", "--")`].

For darwin (at least on MacOS v14.7.2 - M1), it yields a NotADirectoryError / OSError(20, "Not a directory") which fails the test.
For linux, it yields a FileNotFoundError / OSError(2, "File not found") which passes the test.

Ideally, this test should be able to handle it regardless of the machine platform.

See failed test full stacktrace: ​https://dpaste.org/pY48h (link will expire, see result below instead).

FAIL: test_run_formatters_handles_oserror_for_black_path (user_commands.tests.UtilsTests.test_run_formatters_handles_oserror_for_black_path) [FileNotFoundError]
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/user1/.pyenv/versions/3.13.2/lib/python3.13/unittest/case.py", line 58, in testPartExecutor
    yield
  File "/Users/user1/.pyenv/versions/3.13.2/lib/python3.13/unittest/case.py", line 556, in subTest
    yield
  File "/Users/user1/projects/django/tests/user_commands/tests.py", line 584, in test_run_formatters_handles_oserror_for_black_path
    self.assertIn(exception.__qualname__, parsed_error)
    ^^^^^^^
  File "/Users/user1/.pyenv/versions/3.13.2/lib/python3.13/unittest/case.py", line 1174, in assertIn
    self.fail(self._formatMessage(msg, standardMsg))
    ^^^^^^^^^^^
  File "/Users/user1/.pyenv/versions/3.13.2/lib/python3.13/unittest/case.py", line 732, in fail
    raise self.failureException(msg)
    ^^^^^^^^^^^^^^^
AssertionError: 'FileNotFoundError' not found in 'Formatters failed to launch:Traceback (most recent call last):
  File "/Users/user1/projects/django/django/core/management/utils.py", line 175, in run_formatters
    subprocess.run(
    ~~~~~~~~~~~~~~^
        [black_path, "--fast", "--", *written_files],
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        capture_output=True,
        ^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/Users/user1/.pyenv/versions/3.13.2/lib/python3.13/subprocess.py", line 556, in run
    with Popen(*popenargs, **kwargs) as process:
         ~~~~~^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/user1/.pyenv/versions/3.13.2/lib/python3.13/subprocess.py", line 1038, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
    ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                        pass_fds, cwd, env,
                        ^^^^^^^^^^^^^^^^^^^
    ...<5 lines>...
                        gid, gids, uid, umask,
                        ^^^^^^^^^^^^^^^^^^^^^^
                        start_new_session, process_group)
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/user1/.pyenv/versions/3.13.2/lib/python3.13/subprocess.py", line 1974, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
NotADirectoryError: [Errno 20] Not a directory: \'nonexistent\''
​
----------------------------------------------------------------------

Update: Please see ​https://github.com/django/django/pull/19591

[Sarah Boyce]

Mike would you be able to confirm this and that the PR fixes the issue? (See from #36162 you might have a similar setup)