We've announced the deprecation of Python 3.5, intending to break compatibility no sooner than April 2021.

So here are a bunch of small tasks we can take care of when April rolls around:

• Bump the version of Black we use for code formatting
• Bump the tool.black.target-version in pyproject.toml
• Run Black on all the things
• Update our Trove classifiers to drop support for 3.5
• Update CI configuration to stop testing on 3.5
• Update .deb build script to stop building for Debian Stretch and Ubuntu Xenial
• Drop the weird build script bits around dh-systemd
• Drop the dependency constraints for pyjwt / pysaml
• Audit our python package's extras -- I think I recall something in [lint] not supporting 3.5, and that complicating install / contributing docs, maybe?
• Announce to devs that we can finally use f'strings'
• Py 3.6 marked asyncio's API as stable; check if there's anywhere that would make life easier for us
• Py 3.6 introduced a new secrets module to replace os.urandom, see if that would make life easier for us
• Grep source and docs for anything referencing Python 3.5, Stretch, or Xenial and excise it
• Update the minimum version of unpaddedbase64 to 2.1.0 and remove its ignore_missing_imports line from mypy.ini