hereurllib.error.HTTPError: HTTP Error 401: Unauthorized

import urllib.request
url = 'http://example.com'
username = 'user'
password = 'password'
passman = urllib.request.HTTPPasswordMgrWithDefaultRealm()
passman.add_password(None, url, username, password)
auth_handler = urllib.request.HTTPBasicAuthHandler(passman)
opener = urllib.request.build_opener(auth_handler)
urllib.request.install_opener(opener)

ValueError: AbstractBasicAuthHandler does not support the following scheme: 'Negotiate'