from collections import namedtuple

Bread = namedtuple('Bread', 'color')

class ToastException(Exception):
    pass

def toast(bread):
    try:
        put_in_toaster(bread)
    except:
        raise ToastException('Could not toast bread')


def put_in_toaster(bread):
    brad.color = 'light_brown'  # Note the typo


toast(Bread('yellow'))