Activate hassfest requirements CI check (#39940)

Co-authored-by: Franck Nijhof <git@frenck.dev>

.github/workflows/ci.yaml

@@ -518,25 +518,24 @@ jobs:
   hassfest:
     name: Check hassfest
     runs-on: ubuntu-latest
-    needs: prepare-base
+    needs: prepare-tests
+    strategy:
+      matrix:
+        python-version: [3.7]
+    container: homeassistant/ci-azure:${{ matrix.python-version }}
     steps:
       - name: Check out code from GitHub
         uses: actions/checkout@v2
-      - name: Set up Python ${{ env.DEFAULT_PYTHON }}
-        uses: actions/setup-python@v2.1.2
-        id: python
-        with:
-          python-version: ${{ env.DEFAULT_PYTHON }}
-      - name: Restore base Python virtual environment
+      - name:
+          Restore full Python ${{ matrix.python-version }} virtual environment
         id: cache-venv
         uses: actions/cache@v2
         with:
           path: venv
           key: >-
-            ${{ env.CACHE_VERSION}}-${{ runner.os }}-base-venv-${{
-            steps.python.outputs.python-version }}-${{
-            hashFiles('requirements.txt') }}-${{
-            hashFiles('requirements_test.txt') }}-${{
+            ${{ env.CACHE_VERSION}}-${{ runner.os }}-venv-${{
+            matrix.python-version }}-${{ hashFiles('requirements_test.txt')
+            }}-${{ hashFiles('requirements_all.txt') }}-${{
             hashFiles('homeassistant/package_constraints.txt') }}
       - name: Fail job if Python cache restore failed
         if: steps.cache-venv.outputs.cache-hit != 'true'
@@ -546,7 +545,7 @@ jobs:
       - name: Run hassfest
         run: |
           . venv/bin/activate
-          python -m script.hassfest --action validate
+          python -m script.hassfest --requirements --action validate
 
   gen-requirements-all:
     name: Check all requirements