Drop support for Python 3.9

[jacobtylerwalls]

Remove support for launching pylint with Python 3.9.
Code that supports Python 3.9 can still be linted with the --py-version=3.9 setting.

[jacobtylerwalls]

Thankfully UP038 is already deprecated, so I'll just ignore it.

[DanielNoord]

I have never seen this, is this correct? What if we stringify this annotation? Do you still need the type?

[jacobtylerwalls]

I had the same question

[DanielNoord]

Maybe @cdce8p knows?

[jacobtylerwalls]

It's a mypy issue. Rereading the doc I posted in the other comment suggests the workaround in the issue is correct, and these should be changed to TypeAliases. I'll fixup the commit for "Fix UP007" to do that.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.87%. Comparing base (30200e7) to head (38c82af).
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10405      +/-   ##
==========================================
- Coverage   95.91%   95.87%   -0.04%     
==========================================
  Files         176      176              
  Lines       19147    19137      -10     
==========================================
- Hits        18364    18347      -17     
- Misses        783      790       +7     

Files with missing lines	Coverage Δ
pylint/checkers/base/basic_checker.py	98.08% <100.00%> (ø)
pylint/checkers/classes/class_checker.py	93.73% <100.00%> (ø)
pylint/checkers/imports.py	94.86% <100.00%> (ø)
pylint/checkers/refactoring/refactoring_checker.py	98.16% <100.00%> (ø)
pylint/checkers/symilar.py	96.31% <100.00%> (ø)
pylint/checkers/typecheck.py	96.11% <100.00%> (-0.53%)	⬇️
pylint/config/_pylint_config/utils.py	100.00% <100.00%> (ø)
pylint/config/argument.py	100.00% <100.00%> (ø)
pylint/constants.py	100.00% <ø> (ø)
pylint/extensions/code_style.py	100.00% <100.00%> (ø)
... and 7 more

... and 1 file with indirect coverage changes

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