Improve error handling in method that creates Monasca client

Add error handler that prevent crash of forwarded
when agent is not able to connect to keystone

Story: 2007674
Task: 39781
Change-Id: If6366e5b94f9cbe3f21ce9dbeb26d28e3a36ae88

monasca_agent/forwarder/api/monasca_api.py

@@ -18,9 +18,9 @@ import copy
 import json
 import logging
 
-from osc_lib import exceptions
-
+from keystoneauth1.exceptions import base as keystoneauth_exception
 from monascaclient import client
+from osc_lib import exceptions
 
 from monasca_agent.common import keystone
 
@@ -136,6 +136,7 @@ class MonascaAPI(object):
             self._post(tenant_group[tenant], tenant)
 
     def _get_mon_client(self):
+        try:
             k = keystone.Keystone(self._config)
             endpoint = k.get_monasca_url()
             session = k.get_session()
@@ -147,6 +148,8 @@ class MonascaAPI(object):
                 **keystone.get_args(self._config)
             )
             return c
+        except keystoneauth_exception.ClientException as ex:
+            log.error('Failed to initialize Monasca client. {}'.format(ex))
 
     def _send_message(self, **kwargs):
         try: