Should catch extra newlines between import groups

[David Ripton]

Hacking should complain if there's more than one newline between import groups.

For example:

"""
import os

import six
"""

[David Ripton (dripton)]

Launchpad took out my extra newline. The example should read:

"""
import os
<blank line>
<blank line>
import six
"""

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/76559