What is the simplest way of using Python pdb to inspect the cause of an unhandled exception?

gistfile1.py

import functools
import pdb

def debug_on(*exceptions):
    if not exceptions:
        exceptions = (AssertionError, )
    def decorator(f):
        @functools.wraps(f)
        def wrapper(*args, **kwargs):
            try:
                return f(*args, **kwargs)
            except exceptions:
                pdb.post_mortem(sys.exc_info()[2])
        return wrapper
    return decorator

# example

@debug_on(TypeError)
def buggy_function()
    ....
    raise TypeError