Add ZaqarClient "set metadata" help message

ZaqarClient does a full replacement when "set metadata", add help
message to avoid misleading.

Change-Id: I7ea8195a8786e0e530f5ffa9207be752a1eb0577

doc/source/command/queue.rst

@@ -112,7 +112,8 @@ openstack queue set metadata
 
    usage: openstack queue set metadata [-h] <queue_name> <queue_metadata>
 
-Set queue metadata.
+Set queue metadata.All the metadata of the queue will be replaced by 
+queue_metadata.
 
 **Positional arguments:**
 

zaqarclient/queues/v2/cli.py

@@ -48,9 +48,41 @@ class GetQueueStats(cli.GetQueueStats):
     pass
 
 
-class SetQueueMetadata(cli.SetQueueMetadata):
+class SetQueueMetadata(command.Command):
     """Set queue metadata"""
-    pass
+
+    _description = _("Set queue metadata")
+    log = logging.getLogger(__name__ + ".SetQueueMetadata")
+
+    def get_parser(self, prog_name):
+        parser = super(SetQueueMetadata, self).get_parser(prog_name)
+        parser.add_argument(
+            "queue_name",
+            metavar="<queue_name>",
+            help="Name of the queue")
+        parser.add_argument(
+            "queue_metadata",
+            metavar="<queue_metadata>",
+            help="Queue metadata, All the metadata of "
+                 "the queue will be replaced by queue_metadata")
+        return parser
+
+    def take_action(self, parsed_args):
+        client = _get_client(self, parsed_args)
+        queue_name = parsed_args.queue_name
+        queue_metadata = parsed_args.queue_metadata
+        if (client.api_version == 1 and
+                not client.queue(queue_name, auto_create=False).exists()):
+            raise RuntimeError("Queue(%s) does not exist." % queue_name)
+
+        try:
+            valid_metadata = json.loads(queue_metadata)
+        except ValueError:
+            raise RuntimeError("Queue metadata(%s) is not a valid json." %
+                               queue_metadata)
+
+        client.queue(queue_name, auto_create=False).\
+            metadata(new_meta=valid_metadata)
 
 
 class GetQueueMetadata(cli.GetQueueMetadata):