alone class. This addresses the primary concern in
http://bugs.python.org/issue1706815
python-dev discussion here:
http://mail.python.org/pipermail/python-dev/2007-July/073749.html
I chose IOError rather than EnvironmentError as the base class since
socket objects are often used as transparent duck typed file objects
in code already prepared to deal with IOError exceptions.
also a minor fix:
urllib2 - fix a couple places where IOError was raised rather than URLError.
for better or worse, URLError already inherits from IOError so
this won't break any existing code.
test_urllib2net - replace bad ftp urls.