Update CI workflow for Python testing

Author: AndrewSazonov

.github/workflows/ci-testing.yaml

@@ -44,10 +44,13 @@ jobs:
           python-version: ${{ matrix.python-version }}
 
       - name: Upgrade package installer for Python
+        shell: bash
         run: python -m pip install --upgrade pip
 
       - name: Install Python dependencies
+        shell: bash
         run: python -m pip install -r requirements.txt
 
       - name: Run Python tests
+        shell: bash
         run: PYTHONPATH=$(pwd)/src python -m pytest tests/ --color=yes