convert third-party exception to ConnectionError

fixes bug #1207635

Change-Id: I37da522e812286e72706409b8a6d4652515f720f

cinderclient/client.py

@@ -192,7 +192,8 @@ class HTTPClient(object):
             except requests.exceptions.ConnectionError as e:
                 # Catch a connection refused from requests.request
                 self._logger.debug("Connection refused: %s" % e)
-                raise
+                msg = 'Unable to establish connection: %s' % e
+                raise exceptions.ConnectionError(msg)
             self._logger.debug(
                 "Failed attempt(%s of %s), retrying in %s seconds" %
                 (attempts, self.retries, backoff))

cinderclient/exceptions.py

@@ -39,6 +39,11 @@ class EndpointNotFound(Exception):
     pass
 
 
+class ConnectionError(Exception):
+    """Could not open a connection to the API service."""
+    pass
+
+
 class AmbiguousEndpoints(Exception):
     """Found more than one matching endpoint in Service Catalog."""
     def __init__(self, endpoints=None):