more flake8 fixups

.travis.yml

@@ -11,7 +11,7 @@ matrix:
   - python: pypy3
 
 install:
-  - pip install . coverage coveralls flake8 sphinx sphinx-argparse
+  - pip install . black coverage coveralls flake8 sphinx sphinx-argparse
 
 script:
   - make flake

Makefile

@@ -5,7 +5,8 @@ dfm_source_3 := "https://raw.githubusercontent.com/google/diff-match-patch/maste
 all: coverage flake
 
 flake:
-	flake8 tests xmldiff --exclude *diff_match_patch*.py --ignore=E231,E501
+	black --check
+	flake8 tests xmldiff --exclude *diff_match_patch*.py --ignore=E231,E501,W503
 
 coverage:
 	coverage run setup.py test

docs/source/contributing.rst

@@ -15,9 +15,9 @@ Setting Up a Development Environment
 
 To set up a development environment you need a github account, git, and
 of course Python with pip installed. You also should have the Python tools
-``coverage`` and ``flake8`` installed::
+``black``, ``coverage``, and ``flake8`` installed::
 
-  pip install coverage flake8
+  pip install black coverage flake8
 
 Then you need to clone the repository, and install it's dependencies::
 
@@ -44,8 +44,6 @@ The following test runners/commands are known to work:
 
   * ``python setup.py test``
 
-  * ``nosetests``
-
   * ``pytest``
 
 There is no support for ``tox`` to run test under different Python versions.

tests/test_diff.py

@@ -1274,7 +1274,6 @@ def test_sbt_template(self):
 
         result = self._diff(left, right)
 
-        # Most lines get too long and flake8 complains because of this part:
         bm_bm_bm = "/metal:block/metal:block/metal:block"
         self.assertEqual(
             result,