Incorporate black into Chime Lint and Test workflow

Author: grahamalama

.github/workflows/pythonapp.yml

@@ -15,7 +15,6 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
-
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python 3.8
@@ -33,6 +32,11 @@ jobs:
         flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
         # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
         flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+    - name: Check formatting with black
+      run: |
+        # exit if any files still need formatting
+        bash script/format --check
+      continue-on-error: true
     - name: Test with pytest
       run: |
         pip install pytest