Previously, as per most other OpenStack projects, Glance used to rely on an RPC library coming from oslo-incubator. This library graduated from the incubator and was moved into its own project, oslo.messaging. This request for enhancement tracks Glance's adoption of oslo.messaging.
Although the messaging library maintains backwards compatibility with older configuration options, upgrading the configuration files to use the `transport_url` and the new RPC options as necessary is highly recommended. The older configuration options are likely to be removed in future versions of the project.