Add badge and coverage

.github/workflows/python-tests.yml

@@ -17,7 +17,6 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        fail-fast: false
         python-version: [3.6, 3.7, 3.8, pypy3]
 
     steps:
@@ -34,7 +33,9 @@ jobs:
       run: python -m pip install tox tox-gh-actions
     - name: Run Tox
       run: tox
+    - name: Convert coverage
+      run: python -m coverage xml
     - name: Upload coverage to Codecov
       uses: codecov/codecov-action@v1
       with:
-        file: ./coverage.xml
+        fail_ci_if_error: true