pep8: Ignore locale files

Ignore locale files for pep8 gate, otherwise translation jobs
will not merge, see https://review.openstack.org/#/c/97008/

implements bp log-messages-translation-domain-rollout

Change-Id: Ia6ef83997aa68cb9c4e9065c42611a414d9cfdd7
Merge "pep8: Ignore locale files"