[Lint] Use Black to auto-format code

The move to using auto-formatter makes it easier to read, submit and
speeds up development time. https://github.com/ambv/black/

Although I would prefer 79 chars, the default line length of 88 chars
used by black suffices. The flake8 line length remains at 120 chars
since black does not touch comments or docstrings and this will require
another round of fixes.

The only black setting that is not standard is the use of double-quotes
for strings so disabled any formatting of these. Note however that
flake8 will still flag usage of double-quotes. I may change my mind on
double vs single quotes but for now leave them.

A new pyproject.toml file has been created for black configuration.

1 files changed, 22 insertions, 1 deletions

diff --git a/setup.cfg b/setup.cfg
index 9fee85746..8d62dd2a6 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -25,5 +25,26 @@ known_third_party =
     pygtk, gtk, gobject, gtk.gdk, pango, cairo, pangocairo
 known_first_party = msgfmt, deluge
 order_by_type = true
-line_length = 120
 not_skip = __init__.py
+# Black compatible settings
+multi_line_output=3
+include_trailing_comma=True
+force_grid_wrap=0
+line_length=88
+use_parentheses=True
+
+[flake8]
+max-line-length = 120
+builtins = _,_n,__request__
+exclude = .git,.tox,dist,build
+ignore =
+# A003 Class attribute is a python builtin.
+    A003,
+# C813, C815, C816: PY3 missing trailing commas.
+    C813,C815,C816,
+# W503 line break before binary operator.
+    W503,
+    E203
+
+[pycodestyle]
+max-line-length = 88