Run default validator unit tests in github workflow

Author: gkreitz

.github/workflows/python-app.yml

@@ -45,6 +45,9 @@ jobs:
     - name: Run mypy
       run: |
         venv/bin/mypy --non-interactive --config-file mypy.ini -p problemtools
+    - name: Run unit tests for default_validator
+      run: |
+        support/default_validator/test_validator.py
 
   packages: # Use a separate job to test debian packaging to speed things up (no need to test this for every python version above)
     runs-on: ubuntu-latest