gh-154307: Fix tempfile.TemporaryDirectory cleanup on DragonFly BSD

On DragonFly BSD, removing a file or directory with the UF_NOUNLINK flag
fails with EISDIR (IsADirectoryError) instead of EPERM, so the cleanup did
not reset the flags.  Handle IsADirectoryError the same as PermissionError.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: serhiy-storchaka

Lib/tempfile.py

@@ -929,7 +929,8 @@ def __init__(self, suffix=None, prefix=None, dir=None,
     @classmethod
     def _rmtree(cls, name, ignore_errors=False, repeated=False):
         def onexc(func, path, exc):
-            if isinstance(exc, PermissionError):
+            # On DragonFly BSD, UF_NOUNLINK removal fails with EISDIR, not EPERM.
+            if isinstance(exc, (PermissionError, IsADirectoryError)):
                 if repeated and path == name:
                     if ignore_errors:
                         return

Misc/NEWS.d/next/Library/2026-07-21-01-13-39.gh-issue-154307.UNFKL4.rst

@@ -0,0 +1,3 @@
+Fix :meth:`tempfile.TemporaryDirectory.cleanup` on DragonFly BSD, where removing
+a file with the ``UF_NOUNLINK`` flag failed with ``EISDIR`` instead of
+``EPERM``.