Changed target version of black

Author: WisdomPill

tox.ini

@@ -134,7 +134,7 @@ deps_files = dev_requirements.txt
 docker =
 commands =
     flake8
-    black --target-version py38 --check --diff .
+    black --target-version py36 --check --diff .
     isort --check-only --diff .
     vulture redis whitelist.py --min-confidence 80
     flynt --fail-on-change --dry-run .