* Update linting configuration

This removes flake8 in favor of ruff, which also provides isort support, and
updates all files to be black, isort, and ruff compliant. This also adds black
and ruff checks to the tox and Github linting workflow.

* Tweak the code coverage config and calls

* Drop syntax required only for Python 2

* Drop python2-style super() calls

Co-authored-by: Selwin Ong <selwin.ong@gmail.com>

I'd want to advice against using `use_connection()` more, as the
connection setup is less explicit, and also pollutes global memory.

Because, well:

    $ python -m this | head -n4 | tail -n1

;)

Remove sync part of the example.