Solve all flake8 warnings (#163)

Whipper is now fully PEP8 compliant.
Revised version which includes all the changes suggested by Freso.

whipper/command/basecommand.py

@@ -24,6 +24,7 @@ logger = logging.getLogger(__name__)
 # A: The prefix matching prevents passing '-h' (and possibly other
 # options) to the child command.
 
+
 class BaseCommand():
     """
     A base command class for whipper commands.