add linter

.github/workflows/tests.yml

@@ -37,6 +37,13 @@ jobs:
           make install
           python -m pip install .[distribution]
 
+      - name: Lint with flake8
+        run: |
+          # stop the build if there are Python syntax errors or undefined names
+          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: Test with pytest
         run: |
           python -m pytest tests --cov=hyperactive --cov-report=term-missing --cov-report=xml -p no:warnings