Python urllib.urlopen() doesn't work with one of your URLs

If I point Firefox at http://bitbucket.org/tortoisehg/stable/wiki/Home/ReleaseNotes, I get a page of HTML. But if I try this in Python:

import urllib

site = 'http://bitbucket.org/tortoisehg/stable/wiki/Home/ReleaseNotes'\\
req = urllib.urlopen(site)
text = req.read()

I get the following:

500 Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request.

Am I doing something wrong?