Update GitHub Actions workflow to cache virtual environment by python…

… version

.github/workflows/tests.yml

@@ -22,11 +22,11 @@ jobs:
         run: |
           poetry config virtualenvs.create true --local
           poetry config virtualenvs.in-project true --local
-      # - uses: actions/cache@v3
-      #   name: Define a cache for the virtual environment based on the dependencies lock file
-      #   with:
-      #     path: ./.venv
-      #     key: venv-${{ hashFiles('poetry.lock') }}
+      - uses: actions/cache@v3
+        name: Define a cache for the virtual environment based on the dependencies lock file
+        with:
+          path: ./.venv
+          key: venv-${{ matrix.python-version }}-${{ hashFiles('poetry.lock') }}
       - name: Install the project dependencies
         run: poetry install --with test
       - name: Run unit tests