Well its normal that you face such problem while your running first created sis. The exit handler works perfectly in interpreter but the application hangs while exiting in the real application (SIS)
Here is the solution for you
Other thing is the print statements don't show up as there is no console in the application.
In the exit handler you must call appuifw.app.set_exit() for exiting completely (from the embedding Python Shell !)
Requests a graceful exit from the application as soon as the current script execution returns.
Here is a solution:
Hope this helps,
t.add(u'This will work!')