Should've checked other PRs and issues. Apologies.

• Use of deprecated / removed pkg_resources #729
• Fix CI #727
• fix: replace pkg_resources with packaging for setuptools 82+ #737

Upon reviewing, they're both missing some important areas that needed to be addressed (e.g. build-system.requires) for merging. This PR also doesn't convert Cython.__version__ to Version(Cython.__version__) as it's not needed. Lastly, it bounds the packaging version to >=20 which contains the minimal API's needed for what its used for (verified manually).

Note, the CI failures on 3.13.12 (less prominent on 3.13.11) and 3.14.3 (less prominent on 3.14.2) pipelines on test_create_ssl_server_manual_connection_lost when PYTHONASYNCIODEBUG=1 is set is unrelated to this change and seem to be happening in all other open PR's.

These unrelated failures would be fixed by #743

There's generally no point in using packaging to check for cython version. If the user has the correct packaging installed they probably are building using PEP 517 already so the check is redundant personally I'd just remove this code

There's generally no point in using packaging to check for cython version. If the user has the correct packaging installed they probably are building using PEP 517 already so the check is redundant personally I'd just remove this code

Fair, I agree as well 😅. I kept it as-is as that's what pkg_resources was being used for before. Trying to make it as simple as possible for the reviewers...