Ensure package can be built and tested with Python 3.11

[aris-aiven]

Python 3.11 was released recently, and myhoard aims to support it.

[aris-aiven]

The linter error is due to pylint-dev/pylint#6535

[aris-aiven]

The unit test error was due to a change to Enum.format behaviour (see https://docs.python.org/3/whatsnew/3.11.html)

[codecov-commenter]

Codecov Report

Base: 76.22% // Head: 75.81% // Decreases project coverage by -0.40% ⚠️

Coverage data is based on head (e1dbdb7) compared to base (a73efd4).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head e1dbdb7 differs from pull request most recent head fbc241e. Consider uploading reports for the commit fbc241e to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #97      +/-   ##
==========================================
- Coverage   76.22%   75.81%   -0.41%     
==========================================
  Files          16       16              
  Lines        3903     3903              
  Branches      896      917      +21     
==========================================
- Hits         2975     2959      -16     
- Misses        714      733      +19     
+ Partials      214      211       -3     

Impacted Files	Coverage Δ
myhoard/restore_coordinator.py	74.52% <ø> (-0.88%)	⬇️
version.py	0.00% <ø> (ø)
myhoard/controller.py	78.76% <100.00%> (-0.31%)	⬇️
myhoard/basebackup_operation.py	91.21% <0.00%> (-3.42%)	⬇️
myhoard/basebackup_restore_operation.py	80.28% <0.00%> (-0.49%)	⬇️
myhoard/update_mysql_environment.py	0.00% <0.00%> (ø)
myhoard/backup_stream.py	76.94% <0.00%> (+0.31%)	⬆️

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[nicois]

Can we remove support for older python versions too? At least allowing us to use python3.8 syntax would be nice.
Versions of python prior to 3.10 are only receiving security updates; it would be reasonable for us to do likewise.

https://devguide.python.org/versions/

[kmichel-aiven]

The changes are probably all good, but most of them are not described and mixed together in the same commit, this should be split and explained a little more.

[kmichel-aiven]

Can we remove support for older python versions too? At least allowing us to use python3.8 syntax would be nice. Versions of python prior to 3.10 are only receiving security updates; it would be reasonable for us to do likewise.

https://devguide.python.org/versions/

Removing 3.8 and older sounds reasonable.
I wouldn't remove 3.9 since it's still the current version in the latest stable debian (bullseye) and latest RHEL (9).

Python versions pre-3.9 have been deprecated, the PR has been split into smaller commits as requested, and the test matrix was updated to test 3.11 with newer MySQL and Percona Server version.