Add safeguards against Python 3.12

[ischoegl]

Changes proposed in this pull request

Implement safeguards against Python 3.12 in main; the PR replicates similar changes implemented in #1465 for updates of Cantera 2.6. Edit: added a check in SCons to abort attempts that will fail before compiling.

Checklist

• The pull request includes a clear description of this code change
• Commit messages have short titles and reference relevant issues
• Build passes (scons build & scons test) and unit tests address code coverage
• Style & formatting of contributed code follows contributing guidelines
• The pull request is ready for review

[bryanwweber]

Thanks Ingmar! Couple of comments

[ischoegl]

@bryanwweber ... thanks for your comments. Based on feedback, I updated the approach and am now conditioning behavior on the python_sdist and package_build flags: if False, there is only a warning as suggested; if it is True, SCons exits with an error. Also, the safeguards against newer Python versions in setup.cfg are only applied for packaged builds (Edit: there is a pending push, but GH currently has partial outages.).

[bryanwweber]

Thanks for the change @ischoegl! I had one small nitpick from my previous review.

[ischoegl]

@bryanwweber … I believe that all comments are addressed.

[bryanwweber]

Thanks @ischoegl LGTM. One question for my own edification 😄