Format files with black

- Format all files with black
- Update tox.ini flake8 arguments to be compatible
- Add black to requirements-extra.txt
- Reduce ignored flake8 rules and fix a few violations

hscommon/plat.py

@@ -1,8 +1,8 @@
 # Created On: 2011/09/22
 # Copyright 2015 Hardcoded Software (http://www.hardcoded.net)
-# 
-# This software is licensed under the "GPLv3" License as described in the "LICENSE" file, 
-# which should be included with this package. The terms are also available at 
+#
+# This software is licensed under the "GPLv3" License as described in the "LICENSE" file,
+# which should be included with this package. The terms are also available at
 # http://www.gnu.org/licenses/gpl-3.0.html
 
 # Yes, I know, there's the 'platform' unit for this kind of stuff, but the thing is that I got a
@@ -11,6 +11,6 @@
 
 import sys
 
-ISWINDOWS = sys.platform == 'win32'
-ISOSX = sys.platform == 'darwin'
-ISLINUX = sys.platform.startswith('linux')
+ISWINDOWS = sys.platform == "win32"
+ISOSX = sys.platform == "darwin"
+ISLINUX = sys.platform.startswith("linux")