Test failures on Fedora linux

[bkmgit]

When building on Fedora linux Rawhide (40), the test suites that pass are:

• test_graphs.py
• test_md_environ.py
• test_md_table.py
• test_pagetree.py
• test_reader.py
• test_sourceform.py
• test_reader.py Others fail. Can add a containerized Fedora build and test to CI if it would be of interest.

Would also be great to relax dependency version requirements in pyproject.toml to:

markdown-include >= 0.7.0
python-markdown-math >= 0.8
toposort >= 1.7.0
pygments >= 2.12.0
graphviz >= 0.20.0
tqdm >= 4.64.0

[ZedThree]

Oh dear, do they all fail with similar errors? There have been quite a few changes since the last release, so it would be interesting to know if they still fail on current master.

Happy to relax those dependency requirements, though I'll need to double-check none of them have breaking changes.