It also looks as if nova was getting this right:

[root@overcloud-controller-1 ~]# grep periodic_task /usr/lib/python2.7/site-packages/nova* -R
/usr/lib/python2.7/site-packages/nova/manager.py:from oslo_service import periodic_task
/usr/lib/python2.7/site-packages/nova/manager.py:class PeriodicTasks(periodic_task.PeriodicTasks):
/usr/lib/python2.7/site-packages/nova/manager.py:    def periodic_tasks(self, context, raise_on_error=False):
/usr/lib/python2.7/site-packages/nova/manager.py:        return self.run_periodic_tasks(context, raise_on_error=raise_on_error)
/usr/lib/python2.7/site-packages/nova/cells/manager.py:from oslo_service import periodic_task
/usr/lib/python2.7/site-packages/nova/cells/manager.py:    @periodic_task.periodic_task
/usr/lib/python2.7/site-packages/nova/cells/manager.py:    @periodic_task.periodic_task
Binary file /usr/lib/python2.7/site-packages/nova/cells/manager.pyo matches
Binary file /usr/lib/python2.7/site-packages/nova/cells/manager.pyc matches
Binary file /usr/lib/python2.7/site-packages/nova/service.pyo matches
Binary file /usr/lib/python2.7/site-packages/nova/manager.pyo matches
Binary file /usr/lib/python2.7/site-packages/nova/service.pyc matches
Binary file /usr/lib/python2.7/site-packages/nova/scheduler/driver.pyo matches
/usr/lib/python2.7/site-packages/nova/scheduler/manager.py:from oslo_service import periodic_task
/usr/lib/python2.7/site-packages/nova/scheduler/manager.py:    @periodic_task.periodic_task
/usr/lib/python2.7/site-packages/nova/scheduler/manager.py:    @periodic_task.periodic_task(spacing=CONF.scheduler_driver_task_period,
/usr/lib/python2.7/site-packages/nova/scheduler/manager.py:    def _run_periodic_tasks(self, context):
/usr/lib/python2.7/site-packages/nova/scheduler/manager.py:        self.driver.run_periodic_tasks(context)
Binary file /usr/lib/python2.7/site-packages/nova/scheduler/caching_scheduler.pyo matches
/usr/lib/python2.7/site-packages/nova/scheduler/caching_scheduler.py:    def run_periodic_tasks(self, context):
Binary file /usr/lib/python2.7/site-packages/nova/scheduler/manager.pyo matches
Binary file /usr/lib/python2.7/site-packages/nova/scheduler/driver.pyc matches
/usr/lib/python2.7/site-packages/nova/scheduler/driver.py:    def run_periodic_tasks(self, context):
Binary file /usr/lib/python2.7/site-packages/nova/scheduler/caching_scheduler.pyc matches
Binary file /usr/lib/python2.7/site-packages/nova/scheduler/manager.pyc matches
/usr/lib/python2.7/site-packages/nova/rpc.py:from oslo_service import periodic_task
/usr/lib/python2.7/site-packages/nova/rpc.py:class ClientRouter(periodic_task.PeriodicTasks):
/usr/lib/python2.7/site-packages/nova/rpc.py:        self.run_periodic_tasks(nova.context.RequestContext(overwrite=False))
/usr/lib/python2.7/site-packages/nova/rpc.py:    @periodic_task.periodic_task
Binary file /usr/lib/python2.7/site-packages/nova/rpc.pyo matches
/usr/lib/python2.7/site-packages/nova/compute/manager.py:from oslo_service import periodic_task
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task(spacing=CONF.scheduler_instance_sync_interval)
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task(
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task(spacing=CONF.shelved_poll_interval)
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task(spacing=CONF.bandwidth_poll_interval)
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task(spacing=CONF.volume_usage_poll_interval)
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task(spacing=CONF.sync_power_state_interval,
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task(spacing=CONF.update_resources_interval)
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task(
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task(spacing=CONF.image_cache_manager_interval,
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task(spacing=CONF.instance_delete_interval)
/usr/lib/python2.7/site-packages/nova/compute/manager.py:    @periodic_task.periodic_task(spacing=CONF.instance_delete_interval)
Binary file /usr/lib/python2.7/site-packages/nova/compute/manager.pyo matches
Binary file /usr/lib/python2.7/site-packages/nova/compute/manager.pyc matches
/usr/lib/python2.7/site-packages/nova/service.py:            self.tg.add_dynamic_timer(self.periodic_tasks,
/usr/lib/python2.7/site-packages/nova/service.py:    def periodic_tasks(self, raise_on_error=False):
/usr/lib/python2.7/site-packages/nova/service.py:        return self.manager.periodic_tasks(ctxt, raise_on_error=raise_on_error)
Binary file /usr/lib/python2.7/site-packages/nova/rpc.pyc matches
/usr/lib/python2.7/site-packages/nova/network/manager.py:from oslo_service import periodic_task
/usr/lib/python2.7/site-packages/nova/network/manager.py:    @periodic_task.periodic_task
/usr/lib/python2.7/site-packages/nova/network/manager.py:    @periodic_task.periodic_task(
Binary file /usr/lib/python2.7/site-packages/nova/network/manager.pyo matches
Binary file /usr/lib/python2.7/site-packages/nova/network/manager.pyc matches
Binary file /usr/lib/python2.7/site-packages/nova/manager.pyc matches