OverflowError during initialization dates back to the early days of Python:

  http://hg.python.org/cpython/rev/0437738279a8

Integer arithmetic actually did raise OverflowError back then:

>>> 2222222222222 * 22222222222222
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
OverflowError: integer multiplication
>>>

This of course no longer happens, so the whole idea of OverflowError seems
slightly outdated.