[py] Run type checks in CI and report typing coverage to codecov

.github/workflows/python.yml

@@ -45,6 +45,26 @@ jobs:
         env:
           TOXENV: docs
 
+  tox_mypy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout source tree
+        uses: actions/checkout@v2
+      - name: Set up Python 3.7
+        uses: actions/setup-python@v2
+        with:
+          python-version: 3.7.9
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install tox==2.4.1
+      - name: Test with tox
+        run: |
+          tox -c py/tox.ini -- --cobertura-xml-report ci || true
+          bash <(curl -s https://codecov.io/bash) -f py/ci/cobertura.xml
+        env:
+          TOXENV: mypy
+
   unit_tests:
     runs-on: ubuntu-latest
     steps:

py/tox.ini

@@ -15,5 +15,7 @@ commands = flake8 {posargs}
 
 [testenv:mypy]
 skip_install = true
-deps = mypy
-commands = mypy
+deps =
+  mypy
+  lxml
+commands = mypy {posargs}