Move python tool configurations to pyproject.toml, and add the python 3.11 classifier.

[UriyaHarpeness]

• Add missing Programming Language :: Python :: 3.11 classifier for the python package.
• Move pylint config to the pyproject.toml and delete .pylintrc.
• Move mypy config to the pyproject.toml and delete setup.cfg.
• Improve lint_python.py:
  • Reuse and readability.
  • Stop using soon-to-be-deprecated epylint.
  • Use the flags from the pyproject.toml instead of passing them through the CLI.

[UriyaHarpeness]

Hey @trivialfis @hcho3,
While on this subject, I see some flags are being passed in https://github.com/dmlc/xgboost/blob/master/tests/ci_build/lint_python.py, can these flags be removed if they already exist in the pyproject.toml? With perhaps changing the CWD when running the linting script?
It's a shame to have several copies that could get misaligned.

[trivialfis]

For mypy, it should work out of the box. pylint however, is a bit more messy as we haven't upgraded the configuration for a while, the file you referenced is based on some really old and deprecated features from pylint. I can try to upgrade the configuration later.

[UriyaHarpeness]

@trivialfis please let me try to do it myself first, will do so very soon.

[trivialfis]

Thank you for the nice work! Let me know if there's anything I can help.

[UriyaHarpeness]

@trivialfis am I free to use the builtin library pathlib? Would also help simplify this linting script.

[trivialfis]

yup, whatever that comes with python.

[hcho3]

Thanks for working on updating the linting script. Let me know if there's anything I can help.

[UriyaHarpeness]

@hcho3 @trivialfis I think I'm done here, locally everything works.
The only thing I would've maybe done is split the actual linting script and it's configurations, currently it's mixed as seen below:

...
        mypy_results = [
            run_mypy(path)
            for path in [
                # core
                "python-package/",
                # demo
                "demo/json-model/json_parser.py",
                "demo/guide-python/external_memory.py",
                "demo/guide-python/cat_in_the_dat.py",
...

I am very willing to do so, let me know if it's acceptable by you and I shall change it.

PS. The readthedocs issue is unrelated and in progress by you guys: #9115.

[UriyaHarpeness]

@hcho3 @trivialfis poke.

[trivialfis]

Very nice! Now the repository is much more consistent and unified, along with the linting code being cleaned up.

One minor issue mentioned in the comment, otherwise looks good to me.

[UriyaHarpeness]

I think the PR is done now, I'm pretty happy with it.
Now, if I'm the one that should merge it just give me your approvals and I shall do so, otherwise - please go ahead and merge if it's to your liking.
Thanks @trivialfis @hcho3.

[trivialfis]

thank you for your nice work on cleaning up the configuration and helper scripts!

[UriyaHarpeness]

My pleasure! glad I could contribute.
@trivialfis @hcho3