add flake8 action

.github/workflows/lint.yml

@@ -0,0 +1,26 @@
+name: Lint
+
+on:
+  push:
+    paths:
+      - '*.py'
+
+jobs:
+  flake8_py3:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Setup Python
+        uses: actions/setup-python@v1
+        with:
+          python-version: 3.9.9
+          architecture: x64
+      - name: Checkout Stacosys
+        uses: actions/checkout@master
+      - name: Install flake8
+        run: pip install flake8
+      - name: Run flake8
+        uses: suo/flake8-github-action@releases/v1
+        with:
+          checkName: 'flake8_py3'   # NOTE: this needs to be the same as the job name
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}