CI has started failing due to the following error when attempting to run Black:
ImportError: cannot import name '_unicodefun' from 'click' (/home/runner/work/_actions/psf/black/21.12b0/.black-env/lib/python3.8/site-packages/click/__init__.py)The issue is described in Stack Overflow #71673404. But it's only problematic because of being tied to an older version of Black to support ancient Python 2.7 syntax.
We really need to kill off Python 2.7 support; but that's for a separate PR. This just stabilizes things for the time being.