Fix stable oslo-incubator pyflakes.

Change-Id: I685d1dab29e489472d7f97e154665e4e9b12a304
Reviewed-on: https://review.openstack.org/23470
Reviewed-by: James E. Blair <corvus@inaugust.com>
Reviewed-by: Vish Ishaya <vishvananda@gmail.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins