Configuration tweaks fox tox/travis to use and check Black

.travis.yml

@@ -6,6 +6,8 @@ matrix:
       env: TOXENV=py27
     - python: 2.7
       env: TOXENV=lint
+    - python: 3.6
+      env: TOXENV=format-check
     - python: 2.7
       env: TOXENV=docs
 

setup.cfg

@@ -1,2 +1,8 @@
 [flake8]
-ignore = E501,E128,E731,E722
+ignore = 
+  E501,
+  E128,
+  E731,
+  E722,
+  W503  # Black formatter conflict
+  E203  # Black formatter conflict

tox.ini

@@ -28,6 +28,21 @@ deps = flake8
 skip_install = True
 usedevelop = False
 
+
+[testenv:format]
+basepython = python3
+commands = black {posargs} moulinette test
+deps = black
+skip_install = True
+usedevelop = False
+
+[testenv:format-check]
+basepython = {[testenv:format]basepython}
+commands = black {posargs:--check --diff} moulinette test
+deps = {[testenv:format]deps}
+skip_install = {[testenv:format]skip_install}
+usedevelop = {[testenv:format]usedevelop}
+
 [testenv:docs]
 usedevelop = True
 commands = python -m sphinx -W doc/ doc/_build