E-Mail Notifications for 3.7 Automatic Backup Updates

Does anybody know how to configure e-mail notifications for the automatic background update feature that was released with 3.7? I couldn’t find any documentation on wordpress.org, but found the filter below on another site. My goal is to only receive email notifications on failures. I don’t know what to put in the $core_udpate and $result parameters.

apply_filters('auto_core_update_send_email', true, $type, $core_update, $result);