The mock module has been added to Python 3.3 as unittest.mock.
The third party mock module doesn't seem to be maintained anymore.
This is follow up of 72c501454ea33b603918de35565a66dda8abd66a and
add hacking rule to avoid regression issue.
oslotest prepares mock for six in oslotest/__init__.py as follow:
six.add_move(six.MovedModule('mock', 'mock', 'unittest.mock')) and
oslo_messaging/tests/__init__.py imports oslotest before importing
test submodules to setup six.moves for mock, then "from six.moves
import mock" works well.
Note: unittest.mock also detects wrong usage of method
assert_called_once_with.
Change-Id: I3d09733789cfa2550cf47c24f2553357d36bcc0d
4f229832c0