Use tomllib from the standard library on Python 3.11+

[hroncok]

Fallback to tomli, which has the same API.

Fixes https://github.com/tox-dev/tox/issues/2462

Contribution checklist:

(also see CONTRIBUTING.rst for details)

• [x] wrote descriptive pull request text
• [ ] added/updated test(s)
• [ ] updated/extended the documentation
• [x] added relevant issue keyword in message body
• [ ] added news fragment in changelog folder
  • fragment name: <issue number>.<type>.rst for example (588.bugfix.rst)
  • <type> is must be one of bugfix, feature, deprecation, breaking, doc, misc
  • if PR has no issue: consider creating one first or change it to the PR number after creating the PR
  • "sign" fragment with -- by :user:`<your username>`.
  • please, use full sentences with correct case and punctuation, for example:

    Fixed an issue with non-ascii contents in doctest text files -- by :user:`superuser`.
    

  • also see examples
• [x] added yourself to CONTRIBUTORS (preserving alphabetical order)

[jugmac00]

Looks good to me!

But neither tox nor gh actions run Python 3.11.

@gaborbernat What do you think? Are you ok with the changes? This would mean we need to run CI with Python 3.11 beta.

[gaborbernat]

But neither tox nor gh actions run Python 3.11.

Yeah, we need to change that before we merge this. I'll add 3.11 to virtualenv today and then move to tox.

[hroncok]

Is the Python 2 compatibility no longer a concern?

[jugmac00]

Is the Python 2 compatibility no longer a concern?

The information is split between the issue and the pr.

@gaborbernat The Python 2 comp was discussed at https://github.com/tox-dev/tox/issues/2462#issuecomment-1192926874

[gaborbernat]

Seems we'll need to fallback to toml on python 2.

[hroncok]

Yes. See my fixup: Fallback to toml, not tomli, for Python 2 support commit which can still be seen here at github. It seems to have been erased away.

[gaborbernat]

Because you've fallen back to toml on Python 3.11 or less and not just Python 2. 🤔

[hroncok]

So you'd prefer a three-way split? I can do that, I just considered it a bit redundant.

[gaborbernat]

So you'd prefer a three-way split? I can do that, I just considered it a bit redundant.

Yes.

[hroncok]

Looks like 3.5 will also need toml. Will update this later today.

[hroncok]

This seems to work. At least on cpythons.

Let me know if you prefer to use toml also on 3.6 and pin tomli to 2+.

Let me know if you want me to rebase or squash somehow.

[hroncok]

Let me know if you prefer to use toml also on 3.6 and pin tomli to 2+.

I've done that now. Feel free to revert the commit.