Update to Python 3.9 and remove 3.8 support

[Bhairvi23]

Checklist

• No CHANGELOG update needed

• No new tests needed

• No documentation update needed

[mr-tz]

Hey @Bhairvi23, do you want to work on the remaining updates needed for this? Including updating the CI and all code/documentation references to Python 3.8?

[github-actions]

Please add bug fixes, new features, breaking changes and anything else you think is worthwhile mentioning to the master (unreleased) section of CHANGELOG.md. If no CHANGELOG update is needed add the following to the PR description: [x] No CHANGELOG update needed

[williballenthin]

Python 3.8 receives security bug fixes through October of this year. Should we keep support through then or remove support earlier?

https://endoflife.date/python

[mr-tz]

Various other projects / dependencies seem to have moved on already - I'm fine either way though.

[williballenthin]

python 3.10 has some nice new syntax features that i look forward to using. i'm not sure how requiring 3.9 or 3.10 will affect our users. the conservative thing to do would be to keep 3.8 support until that is fully EOL'd.

[Bhairvi23]

Hey @Bhairvi23, do you want to work on the remaining updates needed for this? Including updating the CI and all code/documentation references to Python 3.8?

Yes definitely!

[williballenthin]

lets keep 3.8 around until it goes EOL. then we can reopen and let @Bhairvi23 get this merge.