python coverage: specify dirs, exclude test files (#2473)

* specify dirs, exclude test files

* update comments

* html coverage in CI artifacts

* add destination

* ignore coverage files

* check gym-unity too

.circleci/config.yml

           command: |
             . venv/bin/activate
             mkdir test-reports
-            pytest --cov=mlagents --cov-report xml --junitxml=test-reports/junit.xml -p no:warnings
+            pytest --cov=ml-agents --cov=ml-agents-envs --cov=gym-unity --cov-report html --junitxml=test-reports/junit.xml -p no:warnings
 
       - run:
           name: Check Code Style using pre-commit
       - store_artifacts:
           path: test-reports
           destination: test-reports
+
+      - store_artifacts:
+          path: htmlcov
+          destination: htmlcov

.gitignore

 
 # Code coverage report
 .coverage
+coverage.xml
+/htmlcov/

setup.cfg

+[coverage:run]
+omit = */tests/*
+
-# Run "pytest --cov=mlagents" to see the current coverage percentage.
-# Run "pytest --cov=mlagents --cov-report html" to get a nice visualization of what is/isn't coverge in html format.
+# Run "pytest --cov=ml-agents --cov=ml-agents-envs --cov=gym-unity" to see the current coverage percentage.
+# Run the above plus "--cov-report html" to get a nice visualization of what is/isn't covered in html format.
 fail_under = 60