'Assert that a volume does not belong to the API object under test.
:param BlockDeviceVolume flocker_volume: A volume to check for
membership.
:raise: A test-failing exception if the volume is found in the list of
volumes returned by the API object under test.
:return: ``None`` if the volume is not found in the list of volumes
returned by the API object under test.'

def assert_foreign_volume(self, flocker_volume):

    self.assertNotIn(flocker_volume, self.api.list_volumes())
