500 error returned when an Admin tries to delete membership of image from a non-existent /invalid tenant

Steps to reproduce
1. Add an image to a tenant
$ glance member-add --can-share a2bfa0c3-fb77-4da3-9a45-c0ed0debb1d5 127f00e1254f4efca0088913c8184a41
$ glance member-list --image-id a2bfa0c3-fb77-4da3-9a45-c0ed0debb1d5
+--------------------------------------+----------------------------------+-----------+
| Image ID | Member ID | Can Share |
+--------------------------------------+----------------------------------+-----------+
| a2bfa0c3-fb77-4da3-9a45-c0ed0debb1d5 | 127f00e1254f4efca0088913c8184a41 | True |
+--------------------------------------+----------------------------------+-----------+

2. Try to delete the membership of image from another, or an invalid instance:

Actual result: HTTP 500 Internal Server Error

$ curl -v -H "X-Auth-Token:752ba532d87a4a308587604832e92628" -H "Content-type: application/json" -X DELETE http://myglancehost:9292/v1/images/a2bfa0c3-fb77-4da3-9a45-c0ed0debb1d5/members/112323b253a54736g
* About to connect() to 10.2.3.102 port 9292 (#0)
* Trying 10.2.3.102... connected
> DELETE /v1/images/a2bfa0c3-fb77-4da3-9a45-c0ed0debb1d5/members/1 HTTP/1.1
> User-Agent: curl/7.22.0 (x86_64-pc-linux-gnu) libcurl/7.22.0 OpenSSL/1.0.1 zlib/1.2.3.4 libidn/1.23 librtmp/2.3
> Host: 10.2.3.102:9292
> Accept: */*
> X-Auth-Token:752ba532d87a4a308587604832e92628
> Content-type: application/json
>
< HTTP/1.1 500 Internal Server Error
< Content-Type: text/plain
< Content-Length: 5073
< Date: Wed, 03 Oct 2012 09:37:25 GMT
< Connection: close
<
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/eventlet/wsgi.py", line 382, in handle_one_response
    result = self.application(self.environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 208, in call_func
    return self.func(req, *args, **kwargs)
  File "/opt/stack/glance/glance/common/wsgi.py", line 326, in __call__
    response = req.get_response(self.application)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1053, in get_response
    application, catch_exc_info=False)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1022, in call_application
    app_iter = application(self.environ, start_response)
  File "/opt/stack/keystone/keystone/middleware/auth_token.py", line 278, in __call__
    return self.app(env, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 208, in call_func
    return self.func(req, *args, **kwargs)
  File "/opt/stack/glance/glance/common/wsgi.py", line 326, in __call__
    response = req.get_response(self.application)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1053, in get_response
    application, catch_exc_info=False)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1022, in call_application
    app_iter = application(self.environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 208, in call_func
    return self.func(req, *args, **kwargs)
  File "/opt/stack/glance/glance/common/wsgi.py", line 326, in __call__
    response = req.get_response(self.application)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1053, in get_response
    application, catch_exc_info=False)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1022, in call_application
    app_iter = application(self.environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 208, in call_func
    return self.func(req, *args, **kwargs)
  File "/opt/stack/glance/glance/common/wsgi.py", line 326, in __call__
    response = req.get_response(self.application)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1053, in get_response
    application, catch_exc_info=False)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1022, in call_application
    app_iter = application(self.environ, start_response)
  File "/usr/lib/python2.7/dist-packages/paste/urlmap.py", line 203, in __call__
    return app(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 159, in __call__
    return resp(environ, start_response)
  File "/usr/lib/python2.7/dist-packages/routes/middleware.py", line 131, in __call__
    response = self.app(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 159, in __call__
    return resp(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 208, in call_func
    return self.func(req, *args, **kwargs)
  File "/opt/stack/glance/glance/common/wsgi.py", line 532, in __call__
    request, **action_args)
  File "/opt/stack/glance/glance/common/wsgi.py", line 549, in dispatch
    return method(*args, **kwargs)
  File "/opt/stack/glance/glance/common/utils.py", line 408, in wrapped
    return func(self, req, *args, **kwargs)
  File "/opt/stack/glance/glance/api/v1/members.py", line 70, in delete
    registry.delete_member(req.context, image_id, id)
  File "/opt/stack/glance/glance/registry/__init__.py", line 177, in delete_member
    return c.delete_member(image_id, member_id)
  File "/opt/stack/glance/glance/registry/client.py", line 224, in delete_member
    (image_id, member_id))
  File "/opt/stack/glance/glance/registry/client.py", line 89, in do_request
    action, **kwargs)
  File "/opt/stack/glance/glance/common/client.py", line 63, in wrapped
    return func(self, *args, **kwargs)
  File "/opt/stack/glance/glance/common/client.py", line 374, in do_request
    headers=headers)
  File "/opt/stack/glance/glance/common/client.py", line 80, in wrapped
    return func(self, method, url, body, headers)
  File "/opt/stack/glance/glance/common/client.py", line 511, in _do_request
    raise exception.ServerError()
ServerError: The request returned 500 Internal Server Error.
* Closing connection #0

Expected Result: 404 Not Found for deleting membership from a non-existent or invalid tenant.