Enable colored output for argparse help in Python 3.14

[cdce8p]

Support for colored output was just merged in cpython. Maybe a bit early to add it here already but it doesn't hurt either.

Current	With color

The color output can be disable using various environment variables.
https://docs.python.org/3.14/using/cmdline.html#using-on-controlling-color

[sterliakov]

This certainly looks nice! Are we sure these changes will be present in final 3.14 release? As usual, there's some chance that unreleased functionality may be removed/renamed/significantly altered.

[cdce8p]

Are we sure these changes will be present in final 3.14 release? As usual, there's some chance that unreleased functionality may be removed/renamed/significantly altered.

There is always the possibility that a new feature gets reverted before the final release, though I don't suspect it happening here. Nevertheless if that should happen, a lot of test cases would fail with 3.14 at which point we could just revert this one.

[hamdanal]

Thanks for adding this, I think it is a huge readability upgrade to have colors in the help text of a CLI (the reason I proposed #14455 earlier). I have two suggestions for this change:

1. Please also change dmypy, stubgen and stubtest parsers
2. Instead of branching on the python version and passing a keywords dictionary, set the color attribute on the parser instance after initialization, as it is recommended in the argparse documentation.

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅