In tableauserverclient/server/request_factory.py line 404, myself and a colleague found an issue with the empty_req function within the EmptyRequest class. The issue presented itself when attempting to perform a datasource refresh which uses this function. We believe the empty_req function definition should include the "self" argument in addition to "xml_request". This fix worked for us.

request_factory.py line 404 before the fix:
def empty_req(xml_request):

request_factory.py line 404 after the fix:
def_empty_req(self, xml_request):