How do I prevent exceptions from stopping execution? (global exception handler)

[PyNoob]

By default, uncaught exceptions stop the execution of python scripts (similar to what bash does when -e us set.)

I need to change this behavior, so that the user gets informed about the uncaught exception, but the program continues (like +e in bash).

Reason:
While a programmer can do his best and wrap almost every function into a try... except... statement, there is always the possibility that one forgets such a wrapping. Also, wrapping every line of code in a try... except... statement adds a lot of bloat to the application.

Another reason:
I want to create a GUI application that should display any(!) errors that might occur in a GUI dialog box, rather than "hard crashing" (printing a stack trace and exception to stdout). Simply wrapping the entire main() into a try... except statement would not do the trick because in the case of an error, I could display the error message but I see no apparent way to continue the execution of the GUI app.

So here is some code to make my question more concrete:

#!/usr/bin/env python

import os, sys

print "One"
print "Two" + 1
print "Three"

# Desired output:
#
# One
# An error occured: cannot concatenate 'str' and 'int' objects -- but we are continuing anyway
# Three

# What i do NOT want my code to look like:
# try... except... try... except...

# Perhaps something like the following code can help achieve this goal?

def excepthook(exctype, value, traceback):
"""Prints only the error message as opposed to the full traceback"""
print str(value)
pass

sys.excepthook = excepthook

# BUT HOW CAN I MAKE THIS CONTINUE EXECUTION?