Major buildbot failures caused by this change, eg:

ERROR: test_file (test.test_urllib2net.OtherNetworkTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/buildbot/slave/py-build/2.6.norwitz-amd64/build/Lib/test/test_urllib2net.py", line 126, in test_file
    self._test_urls(urls, self._extra_handlers(), retry=True)
  File "/home/buildbot/slave/py-build/2.6.norwitz-amd64/build/Lib/test/test_urllib2net.py", line 175, in _test_urls
    f = urlopen(url, req, TIMEOUT)
  File "/home/buildbot/slave/py-build/2.6.norwitz-amd64/build/Lib/test/test_urllib2net.py", line 28, in wrapped
    return _retry_thrice(func, exc, *args, **kwargs)
  File "/home/buildbot/slave/py-build/2.6.norwitz-amd64/build/Lib/test/test_urllib2net.py", line 19, in _retry_thrice
    return func(*args, **kwargs)
  File "/home/buildbot/slave/py-build/2.6.norwitz-amd64/build/Lib/urllib2.py", line 391, in open
    response = self._open(req, data)
  File "/home/buildbot/slave/py-build/2.6.norwitz-amd64/build/Lib/urllib2.py", line 409, in _open
    '_open', req)
  File "/home/buildbot/slave/py-build/2.6.norwitz-amd64/build/Lib/urllib2.py", line 369, in _call_chain
    result = func(*args)
  File "/home/buildbot/slave/py-build/2.6.norwitz-amd64/build/Lib/urllib2.py", line 1257, in file_open
    return self.open_local_file(req)
  File "/home/buildbot/slave/py-build/2.6.norwitz-amd64/build/Lib/urllib2.py", line 1291, in open_local_file
    headers, 'file://'+ host + file)
TypeError: cannot concatenate 'str' and 'NoneType' objects