Since this is a new library in 3.4, I can be more flexible.  And since you're talking about adding a new feature (rather than changing or removing an existing feature), this has a vanishingly small chance of screwing anything up.  Therefore I'm okay with adding this feature.

I suppose Python 3.4 only supports platforms that auto-close sockets at the end of a process, but I dimly recall Windows 95/98/ME didn't do that.  And there are crazy people porting to platforms like Amiga.  And I can hardly disapprove of something as wholesome as making sure people call .close().  So if Guido says okay, go ahead and check it in.