openstack-nova in OSP 7 requires python-oslo-serialization.  After upgrading from OSP 6, running nova-manage db sync fails with:

stderr: Traceback (most recent call last):
  File "/usr/bin/nova-manage", line 6, in <module>
    from nova.cmd.manage import main
  File "/usr/lib/python2.7/site-packages/nova/cmd/manage.py", line 65, in <module>
    from oslo_log import log as logging
  File "/usr/lib/python2.7/site-packages/oslo_log/log.py", line 47, in <module>
    from oslo_log import formatters
  File "/usr/lib/python2.7/site-packages/oslo_log/formatters.py", line 24, in <module>
    from oslo_serialization import jsonutils
ImportError: No module named oslo_serialization
Can't determine the existing sync level.
Please ensure the database is running and already initialised.

In version:

openstack-nova-common-2015.1.0-16.el7ost.noarch