style: fix target Python version for Black pre-commit hook

[henryiii]

This fixes a bug in the pre-commit configuration - language-version controls the pre-commit hook, not the black language target. So this was actually targeting the black default language version (2.7 or 3.6 or generic), and it was only working on a machine that had Python 3.7 installed.

[codecov]

Codecov Report

Merging #431 (482c3a8) into main (5a8ae8d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #431   +/-   ##
=======================================
  Coverage   66.88%   66.88%           
=======================================
  Files          11       11           
  Lines         897      897           
=======================================
  Hits          600      600           
  Misses        297      297           

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[henryiii]

This is changing docs/conf.py - we can add it to the ignores if you would prefer it not be changed.

[agronholm]

Why are non-Python files affected?

[henryiii]

Because pre-commit/pre-commit-hooks (end-of-file-fixer, one of the checks at the top) isn't being run in CI.

[agronholm]

Yeah, but pre-commit hooks only run on the files that have changed. Those .rst files weren't supposedly altered by this change.

[henryiii]

I always run pre-commit run -a, which runs on all files. That's also what you are supposed to be running in CI if you use pre-commit (and what pre-commit.ci and pre-commit/action will do). The only-changed part is just for performance, it's not supposed to be invalid, otherwise changing that file will suddenly cause unrelated whitespace changes.

[agronholm]

Interesting. While researching I found that the pre-commit Github action is currently unmaintained and directs to https://pre-commit.ci/ instead. Should I enable that service for this repo?

[henryiii]

I'd recommend it, I really like it (and it's enabled for a few of the other PyPA repos).

[agronholm]

Ok, it's enabled now.

[henryiii]

Took 6.9 seconds. :)

[agronholm]

I should nix the lint build stage as it's redundant now.

[agronholm]

Thanks for this PR and all the extra info. This was quite enlightening.