[python] Docstring typo, test-assertion msgs, maybe_raises improvement, verify_logs helper

[ryan-williams]

Issue and/or context:

• Parent: [python] improve uns DataFrame I/O #2874
• Child: [python] update_uns_by_uri, _update_uns #2876 (uses the new maybe_raises / verify_logs functionality, this was factored from there)

Changes:

• maybe_raises can be passed a str (to match against an error message, regardless of error type) or an (exc, msg) tuple (to match against error type as well as message. As before, this is useful for tests where some cases expect no error, while others want to verify an error's class and/or message.
• tests._util.verify_logs helper, which can verify presence of expected log messages, given a pytest "caplog" fixture

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.03%. Comparing base (1e64fdd) to head (015ad0f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2892      +/-   ##
==========================================
+ Coverage   89.88%   90.03%   +0.15%     
==========================================
  Files          37       37              
  Lines        3925     3925              
==========================================
+ Hits         3528     3534       +6     
+ Misses        397      391       -6     

Flag	Coverage Δ
python	90.03% <ø> (+0.15%)	⬆️

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Components	Coverage Δ
python_api	90.03% <ø> (+0.15%)	⬆️
libtiledbsoma	∅ <ø> (∅)