drop deprecated 'U' open option and fix formatting (Python 3.11 build errors)

[mefuller]

Changes proposed in this pull request

• site_scons/site_tools/subst.py resided to removed deprecated 'U' option which otherwise prevented building with Python 3.11

If applicable, fill in the issue number this pull request is fixing

Closes #1325

If applicable, provide an example illustrating new features this pull request is introducing

Test builds: https://koji.fedoraproject.org/koji/taskinfo?taskID=88565565

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 Mark! Aside from the two comments here, can you move the purely formatting changes into a separate commit and add a .git-blame-ignore-revs file to the root of the repo with that commit hash in it? Thanks!

[mefuller]

@bryanwweber thanks for the review.
Is there a Python 3.11 build that can now be enabled for Cantera CI?

[bryanwweber]

Thanks @mefuller! I pushed a small change to just delete the commented out print and return statements. As far as testing on 3.11 goes, I assume that this will fix the problem. We decided in #1287 not to bump the Python version in CI quite yet, as there are likely to be other spurious failures like this that we can either collect or resolve as we get PRs for them without worrying about the status of the CI suite.

Once CI passes, I think this is good to go.