* Detect neutron.i18n import (neutron._i18n is recommended)
* Check builtins _ usage
* 'builtins = _' in tox.ini is no longer required.
* Introduce hacking rule doctest framework.
Newly added check_builtins_gettext() hacking check takes
token as argument. It is not a good idea to pass a tokenized
line manually. Instead it is reasonable to use docstring based
tests used in hacking repo.
Change-Id: Ib7464658fc4c8a6f1b03af6ab46f0bd3ee0bfb18
44be13a2a6