500 error when tying to attend a meeting

[Chris Johnston]

Traceback (most recent call last):

  File "/srv/django-1.3/django/core/handlers/base.py", line 111, in get_response
    response = callback(request, *callback_args, **callback_kwargs)

  File "/srv/django-1.3/django/contrib/auth/decorators.py", line 23, in _wrapped_view
    return view_func(request, *args, **kwargs)

  File "/srv/summit.ubuntu.com/summit/../summit/schedule/decorators.py", line 42, in inner
    return func(request, summit, attendee, *args, **kwds)

  File "/srv/summit.ubuntu.com/summit/../summit/schedule/decorators.py", line 67, in inner
    return func(request, summit, attendee, *args, **kwds)

  File "/srv/summit.ubuntu.com/summit/../summit/schedule/views.py", line 675, in attend_meeting
    except Participant.DoesNotExist:

NameError: global name 'Participant' is not defined