ResourceFailure exception is created incorrectly

I was trying to set up a Heat DevStack install and the stack creation failed. Instead of an error explaining why it failed, I got the message "Resource create failed: TypeError: __init__() takes at least 3 arguments (2 given)".

Looking through the logs, I found a stack trace explaining a bit more:
2013-08-09 18:11:33.420 5041 TRACE heat.engine.resource Traceback (most recent call last):
2013-08-09 18:11:33.420 5041 TRACE heat.engine.resource File "/opt/stack/heat/heat/engine/resource.py", line 369, in _do_action
2013-08-09 18:11:33.420 5041 TRACE heat.engine.resource while not check(handle_data):
2013-08-09 18:11:33.420 5041 TRACE heat.engine.resource File "/opt/stack/heat/heat/engine/resources/instance.py", line 308, in check_create_complete
2013-08-09 18:11:33.420 5041 TRACE heat.engine.resource return self._check_active(cookie)
2013-08-09 18:11:33.420 5041 TRACE heat.engine.resource File "/opt/stack/heat/heat/engine/resources/instance.py", line 330, in _check_active
2013-08-09 18:11:33.420 5041 TRACE heat.engine.resource raise exception.ResourceFailure(exc)
2013-08-09 18:11:33.420 5041 TRACE heat.engine.resource TypeError: __init__() takes at least 3 arguments (2 given)

You can see at https://github.com/openstack/heat/blob/master/heat/engine/resources/instance.py#L330 that it does indeed call the constructor with only one parameter (two counting self), and from https://github.com/openstack/heat/blob/master/heat/common/exception.py#L275 you can see that it needs at least one more to work.