Add tests for Black, and ignore reformat blame

Change-Id: Ie6c6933a46c4aedf559713d37900ecd617e93885

.git-blame-ignore-revs

@@ -0,0 +1,2 @@
+# Reformat to Black:
+2c62daf54207a4a772c2c5942e4bd88e75d7f463

.zuul.yaml

@@ -1,6 +1,25 @@
+- job:
+    name: adjutant-black-style-check
+    parent: tox
+    description: |
+      Runs black linting tests.
+
+      Uses tox with the ``black`` environment.
+    vars:
+      tox_envlist: black_check
+      test_setup_skip: true
+
+
 - project:
     templates:
       - publish-openstack-docs-pti
       - build-release-notes-jobs-python3
       - openstack-cover-jobs
       - openstack-python3-ussuri-jobs
+    check:
+      jobs:
+        - adjutant-black-style-check
+    gate:
+      queue: adjutant
+      jobs:
+        - adjutant-black-style-check

test-requirements.txt

@@ -9,3 +9,4 @@ doc8>=0.8.0 # Apache-2.0
 mock>=3.0.0 # BSD
 Pygments>=2.2.0 # BSD license
 flake8-bugbear>=19.3.0;python_version>='3.4' # MIT
+black>=19.3b0;python_version>='3.4' # MIT

tox.ini

@@ -52,7 +52,7 @@ commands = sphinx-build -a -E -d releasenotes/build/doctrees -b html releasenote
 [flake8]
 max-line-length = 88
 select = C,E,F,W,B,B950
-ignore = D100,D101,D102,D103,D104,D105,D200,D203,D202,D204,D205,D208,D400,D401,W503,E231,E501
+ignore = D100,D101,D102,D103,D104,D105,D200,D203,D202,D204,D205,D208,D400,D401,W503,E203,E231,E501
 show-source = true
 builtins = _
 exclude=.venv,venv,.env,env,.git,.tox,dist,doc,*lib/python*,*egg,releasenotes,adjutant/api/migrations/*,adjutant/actions/migrations,adjutant/tasks/migrations
@@ -60,3 +60,13 @@ exclude=.venv,venv,.env,env,.git,.tox,dist,doc,*lib/python*,*egg,releasenotes,ad
 [doc8]
 ignore-path=.tox,*.egg-info,doc/build,releasenotes/build,api-ref/build,.eggs/*/EGG-INFO/*.txt,./*.txt,adjutant
 extension=.txt,.rst,.inc
+
+[testenv:black]
+basepython = python3
+commands =
+    black -t py36 .
+
+[testenv:black_check]
+basepython = python3
+commands =
+    black -t py36 --check .