Add RouterNotFoundInRouterFactory exception

Add new exception for l3-agent. It occurs when there is no valid
router_info class which registered in router_factory.

Related-Bug: #1804634
Change-Id: I55a1cb60898ab87ffe137f8c4b0b2f2803bfb219

neutron_lib/exceptions/l3.py

@@ -77,6 +77,11 @@ class RouterNotCompatibleWithAgent(exceptions.NeutronException):
     message = _("Router '%(router_id)s' is not compatible with this agent.")
 
 
+class RouterNotFoundInRouterFactory(exceptions.NeutronException):
+    message = _("Router '%(router_id)s' with features '%(features)s' could "
+                "not be found in the router factory.")
+
+
 class FloatingIpSetupException(exceptions.NeutronException):
     def __init__(self, message=None):
         self.message = message

releasenotes/notes/add-router-not-found-in-factory-exception-e2bf9431549ff9b9.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - Adds new L3 exception ``RouterNotFoundInRouterFactory`` in
+    ``neutron_lib.exceptions.l3``.