Message1653

[OP]
> Note that doing urllib.urlopen('nonexisting') causes an IOError also on RC1
> i.e. the problem appears only when you specify the protocol.

That observation is correct; the problem only appears when you specify a socket-based protocol to urllib.urlopen, e.g. http, ftp, etc.

Urllib.urlopen defaults to the file: protocol if you don't specify one, and so tries to open a local file called "nonexisting", and correctly fails with 

IOError: [Errno 0] No such file or directory: nonexisting

In this circumstance, there is no attempt to create a socket, so the mismapped exception does not occur.