Add support for tomli to parse pyproject.toml

[mattusifer]

PR Summary

PR checklist

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• [ ] Commits respect our guidelines
• [ ] Tests are passing properly (see here on how to run Elpy's tests)

For new features only:

• [ ] Tests has been added to cover the change
• [ ] The documentation has been updated

[gopar]

why remove the built in toml parser? Also you are now forcing a dependency on tomli if we add this in

[mattusifer]

This doesn't remove support for toml, it adds support for tomli. It's not forced, it is imported in the same "optional" way as toml:

try:
    import tomli
except ImportError:
    tomli = None

Currently the toml lib is the only way elpy can parse pyproject.toml files, which makes it required, but toml isn't always in the environment. I think it would make sense to provide other options. Pip itself uses tomli to parse pyproject.toml files, and tomllib (a derivative of tomli) was recently added to the python standard library in 3.11 (so ultimately it will be best to just use that).

This PR isn't ready (yet). I didn't have toml in one of my venvs so I ran into this issue, still figuring out the best way to resolve it generally.

[gopar]

Ah gotcha, completely misread the code. Ping whenever you want a review :)

[steinitzu]

Is anything blocking this? Would love to have this as I currently have to patch my blackutil manually any time I update elpy.

Btw tomli is a dependency of black so imo fine to make it the only option. If you're using black, you have it installed.