Install tox-gh-actions

.github/workflows/tests.yml

@@ -27,7 +27,7 @@ jobs:
         python -m pip install --upgrade pip
         pip install -r requirements.txt
         pip install -r requirements_test.txt
-        pip install tox
+        pip install tox tox-gh-actions
     - name: Tests
       run: |
         tox -r