Dropping support for Python 3.7

[ZedThree]

I'd quite like to start using some Python 3.8 features, notably assignment expressions ("walrus operator"). This would mean dropping support for Python 3.7, which is end of life (EOL) next June (2023).

Ubuntu 18.04, which is also EOL next April (2023), still uses Python 3.6, and that is already EOL, so we technically don't support Ubuntu 18.04 really. The next long-term support Ubuntu version does have Python 3.8.

This would happen in a minor, or perhaps even major, release, either 6.2 or 7.0.

Is anybody still using Python 3.7 (or even 3.6!) and has particularly strong objections to this?