Add 2.7 to tests

.github/workflows/test.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-18.04
     strategy:
       matrix:
-        python-version: ["3.6", "3.7", "3.8", "3.9"]
+        python-version: ["2.7", "3.6", "3.7", "3.8", "3.9"]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2

Makefile

 schema:
 	python setup.py insert_schema
-	$(MAKE) black
 
 black:
 	black -l 90 pi_mqtt_gpio