Should probably pin the version in test_requirements as well, wheel<0.37.1 allows earlier versions.

I wonder why wheel appears in the test_requirements.txt in the first place. Is there a test that builds wheels? Maybe because we use run_tests.py which calls setup.py install and not pip install (which would check the pyproject.toml)?

Anyhow I pinned wheel in the test_requirements.txt and also removed a python3.7 remnant.

Thanks Matti.

Thanks so much everyone for looking into this!

Does this fix the PyPy 3.7 wheel issue as well? That's what originally triggered the bug report.

Does this fix the PyPy 3.7 wheel issue as well?

It would need to be backported to 1.21.x to make a difference as we have dropped 3.7. I will do one more 1.21 release, it would be good if someone could check if this works.