Fix test_decorators issue by setting correct assertLogs levels

[davidhassell]

Fixes #419

See NCAS-CMS/cfdm#197 for details.

[codecov-commenter]

Codecov Report

Merging #424 (7a1f29a) into master (a08ac1f) will increase coverage by 0.46%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #424      +/-   ##
==========================================
+ Coverage   73.80%   74.25%   +0.46%     
==========================================
  Files          85       88       +3     
  Lines       19179    19713     +534     
==========================================
+ Hits        14153    14636     +483     
- Misses       5026     5077      +51     

Flag	Coverage Δ
unittests	74.25% <ø> (+0.46%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
main/cf/domain.py	67.00% <0.00%> (-8.00%)	⬇️
main/cf/constructs.py	91.43% <0.00%> (-4.02%)	⬇️
main/cf/data/partitionmatrix.py	93.34% <0.00%> (-1.53%)	⬇️
main/cf/regrid/regridoperator.py	94.34% <0.00%> (-1.21%)	⬇️
main/cf/dimensioncoordinate.py	68.68% <0.00%> (-0.96%)	⬇️
main/cf/__init__.py	80.71% <0.00%> (-0.87%)	⬇️
main/cf/formula_terms.py	88.38% <0.00%> (-0.48%)	⬇️
main/cf/data/partition.py	85.54% <0.00%> (-0.35%)	⬇️
main/cf/regrid/utils.py	60.39% <0.00%> (-0.04%)	⬇️
main/cf/data/data.py	78.97% <0.00%> (-0.01%)	⬇️
... and 31 more

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[sadielbartholomew]

All good save for a tweak to fix the changelog link. Notably, the full test suite passes locally with both my Python 3.10 and 3.9 conda environments.

You got at the test_decorators fix for cf-python before I could (popped it on my TODO list after completing the cfdm equivalent, to tackle after finishing up more urgent tasks), so thanks since I can tick that off now 😃

Please merge when ready.