Check out an Existing Ticket not work

edit

I 'vejust install a new version of sage from sources to avoid any trouble. The make is ok but when I do git trac checkout 21072, to check out the ticket I obtain

Traceback (most recent call last):
  File "/usr/local/bin/git-trac", line 18, in <module>
    cmdline.launch()
  File "/usr/local/lib/python2.7/dist-packages/git_trac/cmdline.py", line 214, in launch
    app.checkout(args.ticket_or_branch, args.branch_name)
  File "/usr/local/lib/python2.7/dist-packages/git_trac/app.py", line 116, in checkout
    self._checkout_ticket(int(ticket_or_branch), branch_name)
  File "/usr/local/lib/python2.7/dist-packages/git_trac/app.py", line 123, in _checkout_ticket
    ticket = self.trac.load(ticket_number)
  File "/usr/local/lib/python2.7/dist-packages/git_trac/trac_server.py", line 110, in load
    ticket = TracTicket(ticket_number, self.anonymous_proxy)
  File "/usr/local/lib/python2.7/dist-packages/git_trac/trac_ticket.py", line 155, in TracTicket
    change_log = server_proxy.ticket.changeLog(ticket_number)
  File "/usr/lib/python2.7/xmlrpclib.py", line 1243, in __call__
    return self.__send(self.__name, args)
  File "/usr/lib/python2.7/xmlrpclib.py", line 1602, in __request
    verbose=self.__verbose
  File "/usr/lib/python2.7/xmlrpclib.py", line 1283, in request
    return self.single_request(host, handler, request_body, verbose)
  File "/usr/local/lib/python2.7/dist-packages/git_trac/digest_transport_py2.py", line 129, in single_request
    return self.parse_response(response)
  File "/usr/lib/python2.7/xmlrpclib.py", line 1493, in parse_response
    return u.close()
  File "/usr/lib/python2.7/xmlrpclib.py", line 798, in close
    raise ResponseError()
xmlrpclib.ResponseError: ResponseError()

How I can fix it? Thanks Cheers Dominique