It is unfortunate, but on the other hand that's what happens in Python too:

    >>> import sys
    >>> import inspect
    >>> def foo(blah=sys.maxsize): pass
    ... 
    >>> str(inspect.signature(foo))
    '(blah=9223372036854775807)'

Nick proposed something we could use to fix these (I think he called them "named constants") but it's not in the language yet.  Anyway propagating those all the way from Argument Clinic to inspect.Signature would be tricky.

Could you live with this being checked in to 3.4?