• CI now tests Python 3.9, 3.10, 3.11, 3.12, we no longer test 3.5, 3.6, 3.7.
• We no longer advertise support for Python 2.7. This is inevitable as GitHub action runners no longer support Python 2.7, so we can no longer run CI for this version.
• We refer to runners with an explicit version (e.g. macos-13 , no more *-latest). This previously broke most test configurations when macOS defaulted to 14, which is Apple Silicon.
• Add setuptools to install_requires, since on Python 3.12+ this is no longer built-in. The library depends on this at runtime (pkg_resources).

Supersedes #481 and #484. These changes will require a major version bump.