add flake8 job

Make sure that each new contribution passes flake8 checks
only on the diff lines on the actual commit.

Signed-off-by: EstherLerouzic <esther.lerouzic@orange.com>
Change-Id: I55ef4801c6b51109e6b466507cdc00b7ad462b0c

Author: EstherLerouzic

.github/workflows/flake8.yml

@@ -0,0 +1,27 @@
+name: Flake8 Check
+
+on:
+  workflow_call:
+
+jobs:
+  flake8:
+    name: Flake8 on changed Python files
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.10'
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install "flake8>=5.0.4,<6"
+
+      - name: Run flake8 with diff
+        run: |
+          git show HEAD | flake8 -v --diff

.github/workflows/main.yml

@@ -7,6 +7,8 @@ on:
 name: CI
 
 jobs:
+  flake8-check:
+    uses: ./.github/workflows/flake8.yml
   build:
     name: Tox test
     runs-on: ubuntu-latest