Ensure Python packages are avail on linting stage

Author: cytopia

.github/workflows/linting.yml

@@ -31,6 +31,16 @@ jobs:
         with:
           fetch-depth: 0
 
+      - name: Install Python 3.9
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.9'
+
+      - name: Install required Python packages
+        run: |
+          pip install yamllib
+          pip install typing
+
       # ------------------------------------------------------------
       # Lint repository
       # ------------------------------------------------------------