Simplify GitHub action

.github/workflows/python-app.yml

@@ -1,26 +1,20 @@
-name: Python
+name: CI
 
 on:
   push:
-    branches: [ master ]
+    branches:
+      - master
   pull_request:
-    branches: [ master ]
 
 jobs:
+  check-messages:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: kaste/upgrade-messages-test-action@v1
+
   lint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
-    - name: Set up Python 3.8
-      uses: actions/setup-python@v2
-      with:
-        python-version: 3.8
-    - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        pip install flake8 
-    - name: Lint with flake8
-      run: |
-        # stop the build if there are Python syntax errors or undefined names
-        flake8 . --count --show-source --statistics
-        
+    - uses: actions/checkout@v3
+    - uses: TrueBrain/actions-flake8@v2