[1.6.x] Fixed typo in previous commit; refs #21490.

if you specifically wanted the admin view from the admin instance named

``custom``, you would need to call::

    >>> change_url = urlresolvers.reverse('custom:polls_choice_change',

    >>> change_url = urlresolvers.reverse('admin:polls_choice_change',

    ...                                   args=(c.id,), current_app='custom')

For more details, see the documentation on :ref:`reversing namespaced URLs