I think that the select.select calls there are a red herring, since I see no evidence that the rpc socket is ever put in non-blocking mode.
But the line
self.rpcclt.listening_sock.settimeout(10)
indicates that the socket is in timeout mode, and so, the error could be expected if it weren't for the backported fix for issue #9090

I'll have another look at that code and see if thera are any loopholes.

Also, Micahel could try commenting out this line in 
C:\Python27\Lib\idlelib\PyShell.py:
 self.rpcclt.listening_sock.settimeout(10)

and see if the problem goes away.