python-3.10 implements PEP 632 ("Deprecate distutils module"). However, our Windows build currently depends on distutils in order to monkey-patch it: https://github.com/pythongssapi/python-gssapi/blob/main/setup.py#L79-L85

@aiudirog Do you think you'd be able to look into this? We've got some time, but it'll presumably start throwing warnings on 3.10 release.