add linting step

.github/workflows/ci-tests.yml

@@ -8,7 +8,26 @@ on:
       - master
 
 jobs:
+  lint:
+    runs-on: ubuntu-20.04
+    steps:
+      - name: checkout
+        uses: actions/checkout@v2
+      - name: Install Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: 3.9
+      - name: Install lint dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install pre-commit pycodestyle
+      - name: Install and run pre-commit
+        uses: pre-commit/action@v2.0.0
+        with:
+          extra_args: --all-files
   test:
+    needs:
+      - lint
     strategy:
       fail-fast: false
       matrix: