Handle driver exception

Author: zhaoqin-github

f5lbaasdriver/v2/bigip/agent_scheduler.py

@@ -78,6 +78,9 @@ def get_lbaas_agent_hosting_loadbalancer(self, plugin, context,
                         context, plugin, env, gn, lbaas_agent['agent'])
                     if reassigned_agent:
                         lbaas_agent = {'agent': reassigned_agent}
+                    else:
+                        raise lbaas_agentschedulerv2.NoActiveLbaasAgent(
+                            loadbalancer_id=loadbalancer_id)
 
             return lbaas_agent