I tried using special variable $message described here http://www.symfony-project.org/cookbook/1_2/en/error_templates but it seems this variable isn\'t defined
$message
I think I found a much simpler answer. On Symfony 1.4 $message is indeed not defined, but $exception is (it contains the exception object).
$exception
So just echo $exception->message.
$exception->message
Et voilà!