tarfile doesn't set file modes correctly on FreeBSD: test_tarfile.test_modes() fails on FreeBSD

[sorcio]

Bug report

Bug description:

The best example for this is given in the regression test suite. TestExtractionFilters.test_modes in test_tarfiles fails with OSError: [Errno 79] Inappropriate file type or format on FreeBSD.

The reason is that chmod fails with EFTYPE (errno 79) when attempting to set the sticky bit (S_ISVTX) on a file when the effective user is not root. Most other platforms will just ignore the bit in chmod calls.

Tested on FreeBSD 13.2 but documentation suggests this is not a new behavior.

(Note that FreeBSD buildbots haven't been running for a while. This is probably why this issue, although it causes a test failure, hadn't been caught before)

CPython versions tested on:

3.12

Operating systems tested on:

Other

Linked PRs

• gh-108948: tarfile should handle sticky bit in FreeBSD #108950
• gh-108948: Skip test_tarfile.test_modes() on EFTYPE error #109697
• [3.12] gh-108948: Skip test_tarfile.test_modes() on EFTYPE error (#109697) #109698
• [3.11] gh-108948: Skip test_tarfile.test_modes() on EFTYPE error (#109697) #109699

[sorcio]

On further assessment (thanks @encukou), this could be solely a tests issue, and not a library bug. Maybe it's okay that tarfile has different behaviors on different OSes, especially around exotic cases, and it's enough to relax the expectation in the failing test.