To improve testing going forward, this change introduces support for

tox. It's set up to test with 3.9 through 3.14 (but not 3.8, as the

modern license files in our pyproject.toml aren't compatible with the

latest setuptools for 3.8).
Some test-specific issues were caught with tthis on 3.9 and older. We

were asserting on Distribution.name, which wasn't available. This

check isn't really necessary, and has been removed.
To ensure consistency with testing, setuptools has also been updated

to the latest versions available.

Ran tox. All tests pass.