Add Python 3.11 to the testing

[cclauss]

Thanks for submitting a PR!

Please make sure to check for the following items:

• Add unit tests and integration tests where applicable.
  If you've added an error code or changed an error code behavior,
  you should probably add or change a test case file under tests/test_cases/ and add
  it to the list under tests/test_definitions.py.
  If you've added or changed a command line option,
  you should probably add or change a test in tests/test_integration.py.
• Add a line to the release notes (docs/release_notes.rst) under "Current Development Version".
  Make sure to include the PR number after you open and get one.

Please don't get discouraged as it may take a while to get a review.

[cclauss]

Should help to test #608

[cclauss]

On Python 3.11...

Running Sphinx v1.6.2
making output directory...

Exception occurred:
  File "/opt/hostedtoolcache/Python/3.11.0/x64/lib/python3.11/re/_parser.py", line 841, in _parse
    raise source.error('global flags not at the start '
re.error: global flags not at the start of the expression at position 3

https://docs.python.org/3.11/whatsnew/3.11.html

In re Regular Expression Syntax, global inline flags (e.g. (?i)) can now only be used at the start of regular expressions. Using them elsewhere has been deprecated since Python 3.6. (Contributed by Serhiy Storchaka in bpo-47066.)

[cclauss]

@serhiy-storchaka Your thoughts, please?

[Pierre-Sassoulas]

Isn't this co-dependant with #608 ? One of you should probably cherry-pick the change from the other one right ?

[serhiy-storchaka]

Is the full traceback available? This can help identify the regular expression that needs to be corrected.

[samj1912]

The failure was happening in Sphinx. Since we have enabled read the docs PR apps, the doc generation in github actions is no longer needed. A larger term fix would involve updating the Sphinx version (from 1.6.x to 6.0)

Will merge in python 3.11 checks first and then the tomli changes can be merged to test them appropriately.