Upload codecov on condition

Author: iivanou

.github/workflows/tests.yml

@@ -21,7 +21,7 @@ jobs:
     - name: Test with tox
       run: tox
     - name: Upload coverage to Codecov
-      if: matrix.python-version == "3.6" && success()
+      if: matrix.python-version == 3.6 && success()
       uses: codecov/codecov-action@v1
       with:
         files: coverage.xml