Tweaks to the catalog doc and show command

Looks like providing a service id isn't working, so it the help
message was reduced to just type and name.
Added a bit more to the docs, too.

Change-Id: Id7f8b48bdf99773ad55ca7f204f3c779f84633d5

Author: Steve Martinelli

doc/source/command-objects/catalog.rst

@@ -9,6 +9,7 @@ catalog list
 
 List services in the service catalog
 
+.. program:: catalog list
 .. code:: bash
 
     os catalog list
@@ -18,7 +19,12 @@ catalog show
 
 Display service catalog details
 
+.. program:: catalog show
 .. code:: bash
 
     os catalog show
         <service>
+
+.. describe:: <service>
+
+    Service to display (type or name)

openstackclient/identity/v2_0/catalog.py

@@ -68,7 +68,7 @@ def get_parser(self, prog_name):
         parser.add_argument(
             'service',
             metavar='<service>',
-            help=_('Service to display (type, name or ID)'),
+            help=_('Service to display (type or name)'),
         )
         return parser
 
@@ -96,4 +96,9 @@ def take_action(self, parsed_args):
             if 'endpoints_links' in data:
                 data.pop('endpoints_links')
 
+        if not data:
+            self.app.log.error('service %s not found\n' %
+                               parsed_args.service)
+            return ([], [])
+
         return zip(*sorted(six.iteritems(data)))