Add auto-formatter to tox

Author: pganssle

tox.ini

@@ -12,6 +12,17 @@ deps =
 commands =
     python update.py {posargs}
 
+[testenv:format]
+description = Run auto formatters
+skip_install = True
+deps =
+    black
+    isort
+commands =
+    black .
+    isort update.py
+
+
 [testenv:build]
 description = Build a wheel and source distribution
 skip_install = True