protected function doStreamPreparation()
 {
     $tag = common_canonical_tag($this->arg('tag'));
     try {
         $this->peopletag = Profile_list::getByPK(array('tagger' => $this->target->getID(), 'tag' => $tag));
     } catch (NoResultException $e) {
         // TRANS: Client error displayed trying to reference a non-existing list.
         throw new ClientException('No such list.');
     }
     if ($this->peopletag->private && !$this->peopletag->getTagger()->sameAs($this->scoped)) {
         // TRANS: Client error displayed trying to reference a non-existing list.
         throw new AuthorizationException('You do not have permission to see this list.');
     }
 }