tests: Miscellaneous fixes for the test suite

[JDBetteridge]

Encountered when running outside of CI

[codecov]

Codecov Report

❌ Patch coverage is 57.89474% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.53%. Comparing base (0aa772b) to head (2458298).

Files with missing lines	Patch %	Lines
conftest.py	50.00%	2 Missing and 1 partial ⚠️
tests/test_mpi.py	25.00%	3 Missing ⚠️
devito/logger.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2929      +/-   ##
==========================================
- Coverage   83.54%   83.53%   -0.01%     
==========================================
  Files         257      257              
  Lines       53591    53601      +10     
  Branches     4585     4586       +1     
==========================================
+ Hits        44770    44775       +5     
- Misses       8028     8032       +4     
- Partials      793      794       +1     

Flag	Coverage Δ
pytest-gpu-aomp-amdgpuX	68.39% <45.45%> (-0.01%)	⬇️
pytest-gpu-gcc-	78.39% <52.63%> (+<0.01%)	⬆️
pytest-gpu-icx-	78.30% <52.63%> (-0.03%)	⬇️
pytest-gpu-nvc-nvidiaX	69.03% <45.45%> (-0.03%)	⬇️

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

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.