Add lint_and_test github action.

.github/workflows/lint_and_test.yml

@@ -0,0 +1,41 @@
+name: Lint and Test
+
+on: [pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    container:
+      image: fkrull/multi-python
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Set up Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: 3.9
+
+      - name: Cache dependencies
+        uses: actions/cache@v2
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
+
+      - name: Install dependencies
+        run: |
+          pip install -r requirements.txt
+
+      - name: Run tests
+        run: |
+          bash download_fixtures.sh
+          tox
+
+      - name: Upload coverage to GitHub Artifacts
+        uses: actions/upload-artifact@v2
+        with:
+          name: coverage
+          path: htmlcov/