How do I retrieve a JMS Security exception object in SoapUI?

The JMS Status assertion is deactivated. A script assertion was my intention, but I have no idea how to catch the JMSSecurity exception object that is thrown by the AMQ server. If you take a look at the SoapUI source code, you will see that the JMS Status assertion treats the exception (name is jmse), by printing the message inside the exception object to the log. I would want to somehow take that message and to perform some kind of parsing on it (like if the message is: "Username/password used is not valid" than the custom assertion should pass)