Removing a relation from the environment fails

To dupe:
get trunk as of revno 208. Connect to trunk rapi-delta looking at the sample.json file. In the environment view, click on any of the relationship names. Confirm that you want to delete the relationship.

What happens:
The relation line turns orange. Then you see a notification in the notification area saying that the removal failed. The relation never returns to being black until the environment fully redraws. Rapidelta logs report the following error:

2012-10-28 20:22:31,604 juju.rapi.ws:INFO Process message {"op":"remove_relation","endpoint_a":"wordpress:db","endpoint_b":"mysql:db","request_id":17}
2012-10-28 20:22:31,604 juju.rapi.ws:INFO Invoking method <bound method APIContext.remove_relation of <juju.rapi.context.APIContext object at 0x1b529d0>> with {u'endpoint_a': u'wordpress:db', u'endpoint_b': u'mysql:db'}
2012-10-28 20:22:31,605 juju.rapi.ws:INFO Returning results {u'endpoint_a': u'wordpress:db', u'endpoint_b': u'mysql:db', 'log': [], 'err': True, 'failure': 'Traceback (most recent call last):\n File "/home/gary/gui/rapi-delta/juju/rapi/context.py", line 198, in remove_relation\n (endpoint_a, endpoint_b))\n File "/home/gary/gui/rapi-delta/juju/rapi/context.py", line 76, in _invoke\n d = maybeDeferred(func, *args, **kw)\n File "/home/gary/gui/rapi-delta/dev/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 134, in maybeDeferred\n result = f(*args, **kw)\n File "/home/gary/gui/rapi-delta/dev/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 1187, in unwindGenerator\n return _inlineCallbacks(None, gen, Deferred())\n--- <exception caught here> ---\n File "/home/gary/gui/rapi-delta/dev/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 1045, in _inlineCallbacks\n result = g.send(result)\n File "/home/gary/gui/rapi-delta/juju/rapi/cmd/remove_relation.py", line 12, in remove_relation\n raise NoMatchingEndpoints()\njuju.state.errors.NoMatchingEndpoints: No matching endpoints\n', 'request_id': 17, 'op': u'remove_relation'}

What should happen:
 - If there is a server error, the relationship line should turn black again when we hear about it.
 - We should really not see a server error here, of course. It seems we are specifying the relationship endpoints incorrectly.

I'm marking this critical because it potentially affects our user testing.