Fix subprocess coverage tracking with new pytest-cov.

[wRAR]

Extracted, to make sure coverage changes make sense

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.19%. Comparing base (f2556ea) to head (4b83c47).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #231   +/-   ##
=======================================
  Coverage   90.19%   90.19%           
=======================================
  Files          15       15           
  Lines        1030     1030           
  Branches      119      119           
=======================================
  Hits          929      929           
  Misses         80       80           
  Partials       21       21           

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