Python 2.7

>>> import socket
>>> socket.SocketType
<class 'socket._socketobject'>
>>> s = socket.socket()
>>> isinstance(s, socket.SocketType)
True
>>> 


Python 3.4

>>> socket.SocketType
<enum 'SocketType'>
>>> s = socket.socket()
>>> isinstance(s, socket.SocketType)
False
>>> 

SocketType was already present and documented in Python 2 so it should be preserved: http://docs.python.org/2/library/socket.html#socket.SocketType

Also, socket.SocketType and socket.AddressFamily names suggest they should be public but they're not mentioned in the doc.  I think they should just be private though (frankly I fail to understand why a set of constants such as AF_* and SOCK_* should be grouped in a common "container" in the first place).