500 error returned on invalid table name

The following command results in a 500 error in congress. Instead we should return 404 table not found:

nicira@Ubuntu1404Server:~/devstack$ openstack congress datasource table list invalid_name
ERROR: openstack Internal Server Error (HTTP 500) (Request-ID: req-e830229a-27db-4a95-8ee3-889f06fcf220)

2014-09-29 13:42:13.380 ERROR congress.api.application [req-e830229a-27db-4a95-8ee3-889f06fcf220 admin f836b4731b9e483f99274e69f946cd5a] Traceback (most recent call last):
  File "/opt/stack/congress/congress/api/application.py", line 50, in __call__
    response = handler.handle_request(request)
  File "/opt/stack/congress/congress/api/webservice.py", line 319, in handle_request
    return self.list_members(request)
  File "/opt/stack/congress/congress/api/webservice.py", line 345, in list_members
    raise TypeError("Invalid response from data model")
TypeError: Invalid response from data model