Traceback (most recent call last):
  File "/usr/bin/duplicity", line 1403, in <module>
    with_tempdir(main)
  File "/usr/bin/duplicity", line 1396, in with_tempdir
    fn()
  File "/usr/bin/duplicity", line 1247, in main
    action = commandline.ProcessCommandLine(sys.argv[1:])
  File "/usr/lib/python2.7/dist-packages/duplicity/commandline.py", line 999, in ProcessCommandLine
    globals.backend = backend.get_backend(args[0])
  File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 158, in get_backend
    return _backends[pu.scheme](pu)
  File "/usr/lib/python2.7/dist-packages/duplicity/backends/u1backend.py", line 74, in __init__
    self.create_volume()
  File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 323, in iterate
    return fn(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/duplicity/backends/u1backend.py", line 161, in create_volume
    answer = auth.request(self.volume_uri, http_method="PUT")
  File "/usr/lib/python2.7/dist-packages/ubuntuone-couch/ubuntuone/couch/auth.py", line 127, in request
    credentials = get_oauth_credentials()
  File "/usr/lib/python2.7/dist-packages/ubuntuone-couch/ubuntuone/couch/auth.py", line 81, in get_oauth_credentials
    proxy.find_credentials_sync().iteritems())
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 70, in __call__
    return self._proxy_method(*args, **keywords)
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 145, in __call__
    **keywords)
  File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 651, in call_blocking
    message, timeout)
DBusException: org.freedesktop.DBus.Python.ValueError: Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/dbus/service.py", line 707, in _message_cb
    retval = candidate_method(self, *args, **keywords)
  File "/usr/lib/python2.7/dist-packages/ubuntuone-client/ubuntuone/platform/credentials/linux.py", line 210, in find_credentials_sync
    error_handler=decrease_counter_error)
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 137, in __call__
    **keywords)
  File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 584, in call_async
    message.append(signature=signature, *args)
ValueError: Unable to guess signature from an empty dict