warn on bad keys in group

lib/ansible/plugins/inventory/yaml.py

@@ -118,19 +118,22 @@ class InventoryModule(BaseFileInventoryPlugin):
                         raise AnsibleParserError('Invalid "%s" entry for "%s" group, requires a dictionary, found "%s" instead.' %
                                                  (section, group, type(group_data[section])))
 
-            if group_data.get('vars', False):
+            for key in group_data:
+                if key == 'vars':
                     for var in group_data['vars']:
                         self.inventory.set_variable(group, var, group_data['vars'][var])
 
-            if group_data.get('children', False):
+                elif key == 'children':
                     for subgroup in group_data['children']:
                         self._parse_group(subgroup, group_data['children'][subgroup])
                         self.inventory.add_child(group, subgroup)
 
-            if group_data.get('hosts', False):
+                elif key == 'hosts':
                     for host_pattern in group_data['hosts']:
                         hosts, port = self._parse_host(host_pattern)
                         self.populate_host_vars(hosts, group_data['hosts'][host_pattern] or {}, group, port)
+                else:
+                    self.display.warn('Skipping unexpected key (%s) in group (%s), only "vars", "children" and "hosts" are valid' % (key, group))
 
     def _parse_host(self, host_pattern):
         '''