Don't hang when confronted with urls which require authentication

When faced with an url that requires authentication, irkerhook currently blows up rather messily, because urllib.urlopen attempts to prompt the user for a password, which unsurprisingly fails, leading to the hook failing completely with an EOFError .

This changes irkerhook.py to use urllib2 here, so this failure can be detected more easily and the a more sensible answer can be returned.

The debian package currently uses the more heavy-handed "0004-webview.patch" to solve the same problem - http://anonscm.debian.org/viewvc/python-apps/packages/irker/trunk/debian/patches/0004-webview.patch?revision=12689&view=markup