[Python-3000] Traits/roles instead of ABCs

[Bill Janssen]

Alan McIntyre writes:
> I have a nagging concern that these additions will
> clutter up the core, and--no matter how hard you try--adding them is
> going to have an impact on "run-of-the-mill" users of the language.

I don't think that will be the case, if we just use ABCs.  There will
be a definition somewhere of the basic type APIs, but the normal user
will still just say "f=open(FILENAME)" or "d={}" without really caring
what APIs the value returned by "open" or "{}" support -- the current
informal and fuzzy understanding of the type will suffice, just as it
does now.  Those who do care, however, will be able to find out, and
use that information.

Bill