Try out coverage instead of pytest-cov

[A5rocks]

Not sure this will work. Fixes #2645

[codecov]

Codecov Report

Merging #2665 (41b9b02) into master (61775d5) will increase coverage by 0.72%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2665      +/-   ##
==========================================
+ Coverage   98.11%   98.84%   +0.72%     
==========================================
  Files         118      114       -4     
  Lines       16539    16514      -25     
  Branches     3003     3003              
==========================================
+ Hits        16227    16323      +96     
+ Misses        254      134     -120     
+ Partials       58       57       -1     

Impacted Files	Coverage Δ
trio/_core/_tests/test_multierror.py	100.00% <100.00%> (ø)

... and 12 files with indirect coverage changes

[A5rocks]

#2664 has the fix for the Ubuntu 3.11 failure.

[jakkdl]

Nice, the code in testing/ is showing up as covered as expected!

Seems like we've lost coverage of test_multierror_scripts since they're run with subprocess.run. But looks like there's documentation on how to fix that: https://coverage.readthedocs.io/en/7.2.7/subprocess.html
Is the drop in trio/_core/_multierror.py also because of that?

The drop in trio/_tests/test_exports.py seems to be the test timeout on 3.12 so that's not an issue.

[A5rocks]

Wait a second, trio/_core/_tests/test_multierror_scripts/_common.py literally does the thing coverage.py recommends doing. It still doesn't work. What??

[A5rocks]

of course the thing that literally reads the file is not going to work. why did i miss that...

[A5rocks]

welp no clue why the coverage for a few more files isn't working. i give up for now.

[jakkdl]

welp no clue why the coverage for a few more files isn't working. i give up for now.

I suppose we can just exclude trio/_core/_tests/test_multierror_scripts/* from coverage and leave fighting with this for some future crazy person. After that it looks fine for merging!

[jakkdl]

Huh, there's four codecov checks? :o

Anyway, it looks good now - merging~~

[A5rocks]

Huh, there's four codecov checks? :o

... weird. Eh, we can fix that eventually!

[A5rocks]

Ok, the four codecov thing was just cause this was an old PR: #2674 only has 2 checks! (as it should be)