ci: use "--cov-fail-under 100" rather than codecov

Since this project has 100% statement coverage, we can use the simple
pytest-cov command-line option to ensure the project retains full
coverage on all incoming changes. There is no need to involve a remote
service for this.

.github/workflows/tox-test.yml

@@ -45,13 +45,6 @@ jobs:
         run: pip install tox
       - name: Run Tox
         run: tox -e cov
-      - name: Install pytest cov
-        run: pip install pytest-cov
-      - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v2
-        with:
-          fail_ci_if_error: true
-          verbose: true
   docs:
     runs-on: ubuntu-latest
     steps:

tox.ini

@@ -28,7 +28,7 @@ deps=
 	pytest-cov
 usedevelop=true
 commands=
-	pytest --cov-report=html --cov-report=xml --cov=src {posargs}
+	pytest --cov-report=html --cov-report=xml --cov=src --cov-fail-under 100 {posargs}
 
 [testenv:docs]
 deps=