static function ensurePattern($pattern)
 {
     $nb = Nickname_blacklist::getKV('pattern', $pattern);
     if (empty($nb)) {
         $nb = new Nickname_blacklist();
         $nb->pattern = $pattern;
         $nb->created = common_sql_now();
         $nb->insert();
         self::blow('nickname_blacklist:patterns');
     }
 }