Removed support for Python 3.8

[n2ygk]

Description of the Change

Remove Python 3.8 which is EOL per PEP 569

Checklist

• PR only contains one change (considered splitting up PR)
• unit-test added
• documentation updated
• CHANGELOG.md updated (only for user relevant changes)
• author name in AUTHORS

[n2ygk]

drfmaster tests are throwing an error for TypeError for encode of None. Maybe related to #1229?

[sliverc]

There is an upstream change in DRF which caused these errors. I have submitted a PR here encode/django-rest-framework#9615 hope it will be merged soon.

[sliverc]

Thanks for working on this. getting-started.md needs also to be adjusted I think and also add a note in changelog to version 7.1.0 that states that it is the last version supporting 3.7. See how we did it in #1178

[n2ygk]

@sliverc

Thanks for working on this. getting-started.md needs also to be adjusted I think and also add a note in changelog to version 7.1.0 that states that it is the last version supporting 3.7. See how we did it in #1178

Done.

Also, perhaps as a separate PR, should we make a failed drfmaster test a non-fatal workflow error? That's how we do it in DOT, for example: https://github.com/jazzband/django-oauth-toolkit/blob/master/tox.ini#L57-L59. Right now, errors in non-released DRF are blocking successful PRs here.

[n2ygk]

See #1267

[sliverc]

Thanks looks good.