Updated openstack/openstack
Project: openstack/nova  a6dfdbaa68335f5df7055347a12479cddd0d512c

Fix ImportError during docs generation

nova/openstack/common/db/sqlalchemy/test_migrations.py has an
explicit import for lockfile but lockfile is missing from
requirements.txt

Change-Id: I8ae62e5235d0348b9fcc30ef6269089930858aa6