MySQL 5.5.30 introduced a compatibility warning that means an "error" is detected on every run. Refer: http://datacharmer.blogspot.com.au/2013/02/mysql-and-warnings-yet-another.html
The output emailed after every run is below. Workaround is to add '--events' to the opt() array at the top of the 'parse_configuration' function.
From: root <email@example.com>
Subject: ERRORS REPORTED: MySQL Backup error Log for svr-dbms-01 - 2013-05-20_00h20m
Date: Mon, 20 May 2013 00:20:18 +1000
-- Warning: Skipping the data of table mysql.event. Specify the --events option explicitly.