update unit test for build custom message

[lingpri]

Your test only covers the behavior of the buildCustomMessage method. What I'm saying is that buildCustomMessage throws a PermanentEventNotificationException which then gets caught by the try/catch block in execute and replaced with a TemporaryEventNotificationException. If you believe it is right to throw a PermanentEventNotificationException here, then your try/catch block in execute should specifically catch PermanentEventNotificationException and re-throw it rather than wrapping it in a TemporaryEventNotificationException.

Originally posted by @waab76 in #595 (comment)