Ok I figured it out. There is no need to do the following:
encoder = json.JSONEncoder()
ejson = encoder.encode(payload)
However I got another problem now:
E TypeError: Unsupported type "<type 'dict'>" for value "{'first_name': 'Alex', 'id': 5060342395}"
Any idea why the object user in the above payload is being treated as a dictionary?
Thanks