Same type(tuple) is returned by the _get_routing_instance_from_route

method during early returns in case of failure.
Removing next_hop from si_dict if it is not in the route target list.

Closes-Bug: 1579177

Change-Id: Ifb3e127a398b02503193859b5b49a958d6d5348e

src/config/schema-transformer/to_bgp.py

@@ -690,10 +690,10 @@ def _get_routing_instance_from_route(self, next_hop):
             si = _vnc_lib.service_instance_read(fq_name_str=next_hop)
             si_props = si.get_service_instance_properties()
             if si_props is None:
-                return None
+                return (None, None)
         except NoIdError:
             _sandesh._logger.error("Cannot read service instance %s", next_hop)
-            return None
+            return (None, None)
         left_vn_str, _ = get_si_vns(si, si_props)
         if not left_vn_str:
             _sandesh._logger.error("%s: route table next hop service instance "
@@ -1146,7 +1146,7 @@ def set_routes(self, routes=[]):
         rt_list = [route.next_hop for route in routes]
         for route in self.routes or []:
             if route.next_hop not in rt_list:
-                self._si_dict.discard(route.next_hop)
+                del _si_dict[route.next_hop]
         self.routes = routes
         for route in self.routes or []:
             self._si_dict[route.next_hop] = self