Tokens in the custom error message

Thank you very much, sano, patch in #3 works.
This is an obvious bug as tokens are offered to be used in the custom error message, but don't work.
I think this straight-forward fix should be committed.

it is supported in set_error method.

  public function set_error($tokens = array()) {
    $error_element = $this->get_error_element();
    $error_message = t($this->get_error_message());
    $tokens += array(
      '[entity-type]' => $this->rule->entity_type, 
      '[bundle]' => $this->rule->bundle, 
      '[field-name]' => $this->instance['label'], 
      '[value]' => $this->value, 
    );
    $error_message = field_filter_xss(strtr($error_message, $tokens));