Peripheral: add yapf

tox.ini

@@ -6,7 +6,7 @@ envlist =
     ; check,
     {py36},
     ; report,
-    ' docs
+    ; docs
 
 [testenv]
 basepython =
@@ -70,12 +70,14 @@ deps =
     readme-renderer
     pygments
     isort
+    yapf
 skip_install = true
 commands =
     python setup.py check --strict --metadata --restructuredtext
     check-manifest {toxinidir}
     flake8 src tests setup.py
     isort --verbose --check-only --diff --recursive src tests setup.py
+    yapf . --parallel --recursive -i -p --exclude='./dist/*' --exclude='./.tox/*' --exclude='./*.egg-info' --style='{based_on_style: facebook, COLUMN_LIMIT: 120, BLANK_LINE_BEFORE_NESTED_CLASS_OR_DEF: true, ALLOW_SPLIT_BEFORE_DICT_VALUE: false}'
 
 [testenv:report]
 deps = coverage