This is seen in CSIT tests, relevant for Carbon-SR2 candidate validation.

The Robot failure on the candidate: [0].
Reading /restconf/operational/bgp-rib:bgp-rib/rib/example-bgp-rib/peer/bgp:

{IP}

does not show empty RIB, but returns 404 with:
{"errors":{"error":[

{"error-type":"application","error-tag":"data-missing","error-message":"Request could not be completed because the relevant data model content does not exist "}

]}}

Tested on Sandbox, this week link: [1].
It shows that this test can pass [2], but it fails [3] most of the time.
The Sandbox runs contain some debug logs, will analyze later.

[0] https://logs.opendaylight.org/releng/jenkins092/bgpcep-csit-3node-periodic-bgpclustering-ha-only-carbon/403/log.html.gz#s1-s2-t10-k2-k3
[1] https://logs.opendaylight.org/sandbox/jenkins091/bgpcep-csit-3node-periodic-bgpclustering-ha-only-carbon
[2] https://logs.opendaylight.org/sandbox/jenkins091/bgpcep-csit-3node-periodic-bgpclustering-ha-only-carbon/2/log.html.gz#s1-t10-k2-k3
[3] https://logs.opendaylight.org/sandbox/jenkins091/bgpcep-csit-3node-periodic-bgpclustering-ha-only-carbon/9/log.html.gz#s1-t10-k2-k3