Fix 'mapping set' return value

Without this patch, the command 'openstack mapping set <args>' will,
upon success, print the rules for the updated mapping and exit with
return code 1 (failure). This is a problem for scripts and config
management tools that depend on the return code to validate whether the
operation was successful, since even upon success the command returns a
failing error code. Moreover, the behavior of printing the new value is
completely unlike the behavior of any of the 'set' subcommands for
other entities. This patch normalizes the 'mapping set' command by
omitting any return value in the SetMapping take_action() method. This
way the client will only exit with an error code if an exception is
raised, and not upon normal operation.

Change-Id: I610ec3b2fa7561072346d46e49cfc1ae82130e0d

openstackclient/identity/v3/mapping.py

@@ -183,7 +183,6 @@ class SetMapping(command.Command, _RulesReader):
             rules=rules)
 
         mapping._info.pop('links', None)
-        return zip(*sorted(six.iteritems(mapping._info)))
 
 
 class ShowMapping(command.ShowOne):

openstackclient/tests/unit/identity/v3/test_mappings.py

@@ -181,16 +181,12 @@ class TestMappingSet(TestMapping):
         mocker.return_value = identity_fakes.MAPPING_RULES_2
         with mock.patch("openstackclient.identity.v3.mapping."
                         "SetMapping._read_rules", mocker):
-            columns, data = self.cmd.take_action(parsed_args)
+            result = self.cmd.take_action(parsed_args)
         self.mapping_mock.update.assert_called_with(
             mapping=identity_fakes.mapping_id,
             rules=identity_fakes.MAPPING_RULES_2)
 
-        collist = ('id', 'rules')
-        self.assertEqual(collist, columns)
-        datalist = (identity_fakes.mapping_id,
-                    identity_fakes.MAPPING_RULES_2)
-        self.assertEqual(datalist, data)
+        self.assertIsNone(result)
 
     def test_set_rules_wrong_file_path(self):
         arglist = [