def formfield_for_foreignkey(self, db_field, request, **kwargs):
    if ((db_field.name == 'site') and (not request.user.is_superuser)):
        kwargs['queryset'] = self.get_site_list(request)
        kwargs['required'] = True
    return super(MultiSiteCalloutAdmin, self).formfield_for_foreignkey(db_field, request, **kwargs)
def formfield_for_foreignkey(self, db_field, request, **kwargs):
    if ((db_field.name == 'site') and (not request.user.is_superuser)):
        kwargs['queryset'] = self.get_site_list(request)
        kwargs['required'] = True
    return super(MultiSiteCalloutAdmin, self).formfield_for_foreignkey(db_field, request, **kwargs)