Start using Hacking

Instead of blacklisting Hacking globally,
only blacklist those that currently occur frequently
(for a later followup patch), and fix the rest. In
detail:

H101  Use TODO(NAME)
H201  no 'except:' at least use 'except Exception:'
H231  octal number 022 should be written as 0o22
H401  docstring should not start with a space
H701  Empty localization string

Change-Id: Ib3b3d56b68d1cf15d3b67ac9749fcbdb876dc52a