gh-139134: Fix pathlib.Path.copy() Windows privilege errors with copyfile2 fallback

[dynamicy]

• Issue: Fix pathlib.Path.copy() Windows privilege errors with copyfile2 fallback #139134

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[barneygale]

Thanks for this :-)

[barneygale]

Suggested change

	try:
	copyfile2(source_fspath, str(self))
	except OSError as exc:
	winerror = getattr(exc, 'winerror', None)
	if (_winapi is not None and
	winerror in (_winapi.ERROR_PRIVILEGE_NOT_HELD,
	_winapi.ERROR_ACCESS_DENIED)):
	self._copy_from_file_fallback(source, preserve_metadata)
	return
	raise
	try:
	copyfile2(source_fspath, str(self))
	except OSError as exc:
	# Use fallback on ERROR_ACCESS_DENIED
	# or ERROR_PRIVILEGE_NOT_HELD
	if exc.winerror not in (5, 1314):
	raise
	else:
	return

This code is Windows-specific because of the if copyfile2: line above, so we can access exc.winerror directly I think.

We usually hard-code Windows error numbers rather than using _winapi in pathlib - I'm not sure if that's wise but I guess let's be consistent.

[dynamicy]

Thanks—good call. I switched to exc.winerror and check for 5/1314. If we hit either, we fall back to _copy_from_file_fallback; otherwise we re-raise. I also added a tiny comment mapping those to ERROR_ACCESS_DENIED and ERROR_PRIVILEGE_NOT_HELD. Still under the if copyfile2: guard, so Windows-only. Happy to tweak wording or style if you prefer.

[barneygale]

Suggested change

	try:
	import _winapi
	except ImportError:
	_winapi = None

This is unused now

[barneygale]

Suggested change

	if hasattr(exc, "winerror") and exc.winerror in (5, 1314):
	if exc.winerror in (5, 1314):

IIUC winerror is guaranteed to exist for any OSError raised from CopyFile2().

[barneygale]

Suggested change

	Fix ``pathlib.Path.copy()`` failing on Windows when copying files that require elevated privileges (e.g., hidden or system files) by adding a fallback mechanism when ``copyfile2`` encounters privilege-related errors.
	Fix :meth:`pathlib.Path.copy` failing on Windows when copying files that require elevated privileges (e.g., hidden or system files) by adding a fallback mechanism when ``CopyFile2()`` encounters privilege-related errors.