Prepare for enabling H302 rule(services/compute/v3/json)

Currently H302 rule is ignored by tox. However, this rule should
be enabled. This patch partially fixes this problem to prepare for
H302 rule.

Change-Id: I4f573cb306f86cf8476f8fa8950a47c21e443db8
diff --git a/tempest/services/compute/v3/json/keypairs_client.py b/tempest/services/compute/v3/json/keypairs_client.py
index 821b86f..9ca4885 100644
--- a/tempest/services/compute/v3/json/keypairs_client.py
+++ b/tempest/services/compute/v3/json/keypairs_client.py
@@ -15,13 +15,13 @@
 
 import json
 
-from tempest.common.rest_client import RestClient
+from tempest.common import rest_client
 from tempest import config
 
 CONF = config.CONF
 
 
-class KeyPairsV3ClientJSON(RestClient):
+class KeyPairsV3ClientJSON(rest_client.RestClient):
 
     def __init__(self, auth_provider):
         super(KeyPairsV3ClientJSON, self).__init__(auth_provider)