Use em-dash instead of two dashes for 'Issue closed' followup comment

I know this might be tough, as the text is filtered through t(), but is it possible to output an em-dash instead of a double-hyphen in the auto-close message that is put on an issue when it's closed?

Line 559, project_issue.module:

function theme_project_issue_auto_close_message($auto_close_days) {
  $auto_close_interval = format_interval($auto_close_days * 24 * 60 * 60, 2);
  return t('Automatically closed -- issue fixed for !interval with no activity.', array('!interval' => $auto_close_interval));
}

Could we get that '--' changed to an em dash somehow? It would be more semantically correct (see http://www.grammarbook.com/punctuation/dashes.asp and http://www.alistapart.com/articles/emen/)... and less of a bother to this grammar nazi's eyes :D