Add black to tox

.circleci/config.yml

@@ -88,7 +88,7 @@ jobs:
       - run: *install_dependencies
       - run:
           name: run linter
-          command: TOXENV=flake8 tox
+          command: tox -e flake8,black
       - save_cache: *save_cache_settings
 
 

tox.ini

@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py27, py36, flake8
+envlist = py27, py36, flake8, black
 
 [pytest]
 addopts =
@@ -23,3 +23,7 @@ deps =
     flake8==3.6.0
 commands =
     flake8 mozetl tests
+
+[testenv:black]
+deps = black
+commands = black --check mozetl/ tests/