Upper pin markupsafe

[MetRonnie]

ImportError: cannot import name 'soft_unicode' from 'markupsafe'

Jinja2 @ 2.11.3 has a dependency MarkupSafe>=0.23. Unfortunately Pallets have made a breaking change in the API in MarkupSafe 2.1.0, but have no plans to patch version 2.11 of Jinja2 with an upper pin on MarkupSafe, so we have to do it ourselves.

pallets/jinja#1585

Note: we have discussed moving to version 3.0 of Jinja2, which is the only supported version going forward (see comments from the Pallets team on the issue above). The difficulty is convincing ourselves this will not introduce breaking changes to Cylc workflows that are dependent on Jinja2. It is is unfeasible (and not our job) to write a test spec for Jinja2; however, it might be enough to have a suitably complex test workflow that we can diff with a reference file to see if Jinja2 updates cause changes in output.

Requirements check-list

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg and conda-environment.yml.
• Does not need tests
• Appropriate change log entry included.
• (master branch) I have opened a documentation PR: Add note on markupsafe cylc-doc#408

[MetRonnie]

• conda builds / test_conda_install failing on master also, fix in main loop: fix log_main_loop and add log_db plugin #4674
• manylinux-compatibility / test failing for Python 3.9 - not sure why

[oliver-sanders]

The manylinux failure is due to a combination of kiwisolver dropping manylinux1 support and pip22 failing on error (so no longer falling back to the previous version as it used to).

The (transient) kiwisolver dep is kiwisolver>=1.0.1, manylinux support was only dropped at the most recent 1.3.2 release so we are good here, for now...

This might be enough to patch things over for now #4704

[wxtim]

Annoying, but valid·