http://docs.python.org/library/socket.html#socket.error
"Changed in version 2.6: socket.error is now a child class of IOError."

However, this is not the case.

$ python
Python 2.7.2 (default, Aug 18 2011, 18:26:35) 
[GCC 4.1.2 20080704 (Red Hat 4.1.2-50)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import socket
>>> isinstance( socket.error, IOError )
False


Catching IOError in except blocks does not catch socket.error, as one might expect according to the documentation.