Migrate poll : to avoid duplication messages related to primary keys

In migrate/plugins/destinations/poll.inc at public function complete()
To avoid duplication messages related to primary keys in the table poll_vote I changed

db_insert('poll_vote')
  ->fields(array(
    'chid' => $chid,
    'nid' => $entity->nid,
    'uid' => $vote['uid'],
    'hostname' => $vote['hostname'],
    'timestamp' => $vote['timestamp'],
  ))
  ->execute();

Into

$migration = Migration::currentMigration();
try {
  db_insert('poll_vote')
    ->fields(array(
       'chid' => $chid,
       'nid' => $entity->nid,
       'uid' => $vote['uid'],
       'hostname' => $vote['hostname'],
       'timestamp' => $vote['timestamp'],
     ))
     ->execute();
 } catch (Exception $e) {
   // If we catch any errors here, save the messages.
   $migration->saveMessage($e->getMessage());
 }