fix: safely handle restrictive directory cleanup and close scandir iterator (fixes #15169)

[saifmodan2006]

Summary

Fixes #15169.

When test suites create directories with restrictive modes such as 0o000 (for example, tests exercising non-browseable or permission-denied directories), pytest's subsequent cleanup of numbered directories (cleanup_numbered_dir -> rm_rf(garbage)) could fail with OSError: [Errno 39] Directory not empty or leak unclosed scandir iterators resulting in PytestUnraisableExceptionWarning. When running test suites with -W error, this warning would turn into an unhandled exception during session finish, causing clean test runs to fail.

Changes Made

1. src/_pytest/pathlib.py:

   • on_rm_rf_error:
     • Handle IsADirectoryError and (func in (os.unlink, os.remove) and p.is_dir()): when directory traversal was unable to identify a directory (e.g. restrictive permissions on POSIX), chmod the entry and recursively remove it with rm_rf(p).
     • Handle ENOTEMPTY / EEXIST when func is os.rmdir: if removing a parent directory fails because child entries were skipped due to restrictive permissions, grant _chmod_rwx across the directory tree and retry removal.
   • rm_rf:
     • Call _chmod_rwx(str(path)) at the start of rm_rf so the target directory has read/write/exec permissions before shutil.rmtree traversal begins.
   • find_prefixed:
     • Wrap os.scandir(root) with a with os.scandir(root) as it: context manager to ensure the ScandirIterator is properly finalized and closed, preventing ResourceWarning: unclosed scandir iterator on Python 3.14+.
   • Imported ENOTEMPTY and EEXIST from errno.

2. testing/test_tmpdir.py:

   • Added test_on_rm_rf_error_is_a_directory_error: verifies IsADirectoryError is handled cleanly by on_rm_rf_error without warnings.
   • Added test_on_rm_rf_error_directory_not_empty: verifies ENOTEMPTY on os.rmdir triggers recursive chmod and cleanup without warnings.
   • Added test_find_prefixed_closes_scandir_iterator: verifies find_prefixed closes the scandir iterator without emitting ResourceWarning.

Testing

• Ran full testing/test_tmpdir.py: 53 passed, 9 skipped.
• Ran full testing/test_pathlib.py: 113 passed.
• All new regression tests pass cleanly.

[0xamlab]

Verified this on macOS with Python 3.14.6. The three new regression tests in testing/test_tmpdir.py pass in 1.06s (3 passed). On main, the same scenarios fail: on_rm_rf_error(os.unlink, subdir, IsADirectoryError()) returns False, leaves the directory, and emits a PytestWarning; the ENOTEMPTY path behaves the same. The fix at src/_pytest/pathlib.py:128 routes directory-unlink errors into rm_rf, and src/_pytest/pathlib.py:137 chmods and re-tries when os.rmdir hits ENOTEMPTY/EEXIST. find_prefixed at src/_pytest/pathlib.py:243 now closes the scandir iterator with a context manager.