Committed to py3k in r84098.   Accepting this change for py3k was an easy decision to make because zip and map already behave this way in 3.x.

I am inclined to reject this for 2.7, however.  While I agree that this is a bug, fixing it has a potential of breaking users' code.  I also note that for zip and map, 2.7 users can switch to izip and imap which don't have this problem.  Arguably, switching to izip and imap in new code is a good idea regardless of this issue.  While there is no similar work-around for reduce, I don't think this bug is important enough to introduce backward incompatible change in the stable series.