When IDLE cannot connect to its subprocess, it tries to display the 
socket.error. But since python 3.0 the exception variable is cleared 
after the "except:" block and unavailable for the displaying code.

Exception in thread SockThread:
Traceback (most recent call last):
  File "c:\dev\python\py3k\lib\threading.py", line 507, in 
_bootstrap_inner
    self.run()
  File "c:\dev\python\py3k\lib\threading.py", line 462, in run
    self._target(*self._args, **self._kwargs)
  File "c:\dev\python\py3k\lib\idlelib\run.py", line 125, in 
manage_socket
    show_socket_error(err, address)
UnboundLocalError: local variable 'err' referenced before assignment

Patch is attached.