Crash on confirming non-existing email address

One-sentence description

Current behaviour

500 error

Expected behaviour

404 not found

Steps to reproduce

1. Go to /registration/confirm-email/some-uuid

Note that it should be a UUID inside the url!

Stacktrace

File "/usr/local/lib/python3.5/site-packages/django/core/handlers/exception.py" in inner
 35.             response = get_response(request)

File "/usr/local/lib/python3.5/site-packages/django/core/handlers/base.py" in _get_response
 128.                 response = self.process_exception_by_middleware(e, request)

File "/usr/local/lib/python3.5/site-packages/django/core/handlers/base.py" in _get_response
 126.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/usr/local/lib/python3.5/site-packages/django/views/generic/base.py" in view
 69.             return self.dispatch(request, *args, **kwargs)

File "/usr/local/lib/python3.5/site-packages/django/views/generic/base.py" in dispatch
 89.         return handler(request, *args, **kwargs)

File "./registrations/views.py" in get
 100.             emails.send_new_registration_board_message(entry.get())

File "/usr/local/lib/python3.5/site-packages/django/db/models/query.py" in get
 403.                 self.model._meta.object_name

Exception Type: DoesNotExist at /registration/confirm-email/33c721a7-c032-407b-82a0-2f81c4061804/
Exception Value: Entry matching query does not exist.