Handle non-iterables for `ntpath.commonpath`

[nineteendo]

Bug report

Bug description:

>>> import ntpath
>>> ntpath.commonpath(None)
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "<frozen ntpath>", line 826, in commonpath
ValueError: commonpath() arg is an empty sequence

Expected: TypeError: 'NoneType' object is not iterable like for posixpath.commonpath.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-117335: Handle non-iterables for ntpath.commonpath #117336

[serhiy-storchaka]

For reference, posixpath.commonpath() was changed in #114709. I forget to check also the ntpath implementation. 🤦‍♂️

[nineteendo]

Yeah, I saw when your test failed when I changed posixpath.commonpath().
But don't feel too bad, it happens to the best of us.

[nineteendo]

Maybe we could create test_os_path.py for common tests between ntpath & posixpath?
That would've probably caught this earlier.

[serhiy-storchaka]

Common tests are already defined in test_genericpath.CommonTest.