import sys

class Test(Exception):
    def check(self, tag):
        print("%s.__traceback__ before raise: %s" % (tag, [self.__traceback__]))
        return self

    def __setattr__(self, name, value):
        print("Also note that we can't observe %s changing to %s" % (name, value))
        return super().__setattr__(name, value)

try:
    raise Test("thing1").check("a")
except Exception as a:
    print("a.__traceback__ after raise : %s" % [a.__traceback__])
    try:
        raise Test("thing2").with_traceback(a.__traceback__).check("b") from a
    except Exception as b:
        print("b.__traceback__ after raise : %s" % [b.__traceback__])

# produces output like:
# a.__traceback__ before raise: [None]
# a.__traceback__ after raise : [<traceback object at 0x7f95c5a21708>]
# b.__traceback__ before raise: [<traceback object at 0x7f95c5a21708>]
# b.__traceback__ after raise : [<traceback object at 0x7f95c5a21748>]