add looser tolerance to coverage action

Author: phobson

.github/workflows/check-test-coverage.yml

@@ -20,6 +20,7 @@ jobs:
         pip install pytest pytest-cov pytest-mpl coverage docopt
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
         pip install scipy
+        export MPL_IMGCOMP_TOLERANCE=20
         coverage run --source probscale check_probscale.py --doctest-modules --mpl --cov-report=xml
     - name: Upload coverage to Codecov
       uses: codecov/codecov-action@v1