Add check to the flake8 job
Add check to the flake8 job

Follow up recommendation of [1].
[1] http://lists.openstack.org/pipermail/openstack-dev/2018-June/131233.html

Change-Id: Id268be8b32ce870f2f04fa8a52f4f1854a613fa7

mahak/cinder,openstack/cinder,openstack/cinder,mahak/cinder