Add more checks

- python code formatting is tested with yapf
- cron workflow to run cargo audit
- Don't run on latest

.github/workflows/python.yml

@@ -0,0 +1,44 @@
+name: pylint
+on:
+  push:
+    paths:
+      - '**/*.py'
+      - '.pylintrc'
+      - '!third_party/**'
+  pull_request:
+    types: [opened, synchronize, reopened]
+jobs:
+  pylint:
+    runs-on: ubuntu-18.04
+    strategy:
+      matrix:
+        python-version: [3.6, 3.7, 3.8]
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v1
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip setuptools wheel
+          pip install tockloader
+      - name: Test code with pylint
+        run: |
+          pip install pylint
+          pylint --rcfile=.pylintrc --score=n `find . ! -path "./third_party/*" -type f -name '*.py'`
+
+  yapf:
+    runs-on: ubuntu-18.04
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up Python 3.7
+        uses: actions/setup-python@v1
+        with:
+          python-version: 3.7
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip setuptools wheel
+          pip install yapf
+      - name: Test code formatting with yapf
+        run: yapf --style=chromium --recursive --exclude third_party --diff .