gh_action: fix python lint

.github/workflows/python_lint.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [2.7, 3.5, 3.6, 3.7]
+        python-version: [2.7, 3.5, 3.6, 3.7, 3.8]
 
     steps:
       - name: Checkout
@@ -24,9 +24,10 @@ jobs:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
         run: |
+          export IDF_PATH=${GITHUB_WORKSPACE}
           pip install --upgrade pip
           pip install -r requirements.txt
       - name: Lint with flake8
         run: |
           pip install flake8
-          flake8 . --config=.flake8
+          flake8 . --config=.flake8 --benchmark