Plays and tasks now yell when they see parameters they do not understand, so that typos like 'var' for 'vars'

don't result in people having to ask questions about what is wrong with their playbook

lib/ansible/playbook/task.py

@@ -26,9 +26,19 @@ class Task(object):
         'play', 'notified_by', 'tags', 'with_items', 'first_available_file'
     ]
 
+    # to prevent typos and such
+    VALID_KEYS = [
+         'name', 'action', 'only_if', 'async', 'poll', 'notify', 'with_items', 'first_available_file',
+         'include', 'tags'
+    ]
+
     def __init__(self, play, ds, module_vars=None):
         ''' constructor loads from a task or handler datastructure '''
 
+        for x in ds.keys():
+            if not x in Task.VALID_KEYS:
+                raise errors.AnsibleError("%s is not a legal parameter in an Ansible task or handler" % x)
+
         self.module_vars = module_vars
         self.play        = play