DM-40151: Fix bug in ImportTestCase

[timj]

Also some other cleanups.

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

Patch coverage: 91.30% and project coverage change: +0.03 🎉

Comparison is base (4b479e1) 93.97% compared to head (256fa23) 94.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #166      +/-   ##
==========================================
+ Coverage   93.97%   94.00%   +0.03%     
==========================================
  Files          44       44              
  Lines        2870     2853      -17     
==========================================
- Hits         2697     2682      -15     
+ Misses        173      171       -2     

Impacted Files	Coverage Δ
python/lsst/utils/tests.py	78.87% <60.00%> (+0.44%)	⬆️
python/lsst/utils/classes.py	100.00% <100.00%> (ø)
python/lsst/utils/packages.py	89.84% <100.00%> (-0.06%)	⬇️
python/lsst/utils/timer.py	99.23% <100.00%> (-0.04%)	⬇️
python/lsst/utils/wrappers.py	91.24% <100.00%> (-0.37%)	⬇️
tests/test_getTempFilePath.py	100.00% <100.00%> (ø)
tests/test_timer.py	100.00% <100.00%> (ø)

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