[wip] Add pylint and fix pylint issues

.github/workflows/unittest.yml

@@ -12,6 +12,11 @@ jobs:
     steps:
     - name: Checkout
       uses: actions/checkout@v2
+    - name: Lint
+      run: |
+        pip3 install --upgrade pip wheel setuptools
+        pip3 install pylint
+        python3 -m pylint check_http_json.py
     - name: Unit Test
       run: |
         python3 -m unittest discover