The following doctest should pass, but it fails:

    >>> def spam(): print("eggs")
    ...
    >>> assert spam()
    eggs
    Traceback (most recent call last):
    AssertionError

But if we remove the print output from printed results the test pass:

    >>> def spam(): print("eggs")
    ...
    >>> assert spam()
    Traceback (most recent call last):
    AssertionError

I'm writing the 2nd edition of a book about Python (covering python3) and Django and I'm using doctest to run the interactive sessions that I use as examples in book.