pythongh-108962: Skip test_tempfile.test_flags() if not supported

Skip test_tempfile.test_flags() if chflags() fails with "OSError:
[Errno 45] Operation not supported" (ex: on FreeBSD 13).

Lib/test/test_tempfile.py

@@ -1837,6 +1837,20 @@ def test_modes(self):
     @unittest.skipUnless(hasattr(os, 'chflags'), 'requires os.lchflags')
     def test_flags(self):
         flags = stat.UF_IMMUTABLE | stat.UF_NOUNLINK
+
+        # skip the test if these flags are not supported (ex: FreeBSD 13)
+        filename = TESTFN
+        try:
+            open(filename, "w").close()
+            try:
+                os.chflags(filename, flags)
+            except OSError as exc:
+                # "OSError: [Errno 45] Operation not supported"
+                self.skipTest("chflags() doesn't support "
+                              "UF_IMMUTABLE|UF_NOUNLINK: {exc}")
+        finally:
+            support.unlink(filename)
+
         d = self.do_create(recurse=3, dirs=2, files=2)
         with d:
             # Change files and directories flags recursively.

Misc/NEWS.d/next/Tests/2023-09-05-23-00-09.gh-issue-108962.R4NwuU.rst

@@ -0,0 +1,3 @@
+Skip ``test_tempfile.test_flags()`` if ``chflags()`` fails with "OSError:
+[Errno 45] Operation not supported" (ex: on FreeBSD 13). Patch by Victor
+Stinner.