Update error messages in sanity tests

Update error messages throughout sanity tests
to use the same (or similar) format of error message.

Change-Id: I4db0517a5b264151ddaa6ea2c2a04d37e139944e
Related-PROD: #PROD-32415
diff --git a/test_set/cvp-sanity/tests/test_rabbit_cluster.py b/test_set/cvp-sanity/tests/test_rabbit_cluster.py
index d0bb44b..f90c54f 100644
--- a/test_set/cvp-sanity/tests/test_rabbit_cluster.py
+++ b/test_set/cvp-sanity/tests/test_rabbit_cluster.py
@@ -44,9 +44,9 @@
         if required_cluster_size_dict[node] != running_nodes_count:
             control_dict.update({node: running_nodes_count})
 
-    assert not len(control_dict), "Inconsistency found within cloud. " \
-                                  "RabbitMQ cluster is probably broken, " \
-                                  "the cluster size for each node " \
-                                  "should be: {} but the following " \
-                                  "nodes has other values: {}".format(
-        len(required_cluster_size_dict.keys()), control_dict)
+    assert not len(control_dict), (
+        "RabbitMQ cluster is probably "
+        "broken - the cluster size for each node should be ({}),\nbut the "
+        "following nodes have other values:\n{}".format(
+            len(required_cluster_size_dict.keys()), control_dict)
+    )