Return appropriate error message when route prefix cannot be parsed

Change-Id: I5f518d661d916d7eff4b1857e7bd5a45e01f6094
Closes-Bug: 1609728
(cherry picked from commit f4466d7)

src/config/api-server/vnc_cfg_types.py

@@ -1971,7 +1971,10 @@ def _check(cls, obj_dict, db_conn):
         family = None
         entries = obj_dict.get('aggregate_route_entries', {})
         for route in entries.get('route', []):
-            route_family = IPNetwork(route).version
+            try:
+                route_family = IPNetwork(route).version
+            except TypeError:
+                return (False, (400, 'Invalid route: %s' % route))
             if family and route_family != family:
                 return (False, (400, 'All prefixes in a route aggregate '
                                 'object must be of same ip family'))