API - LayoutRegionMediaEdit not working?

Can anyone explain me why this code does not work?
Returned status = ERROR

params = [(‘layoutid’, ‘8’),
(‘regionid’, ‘56d9a61cf1dc5’),
(‘mediaid’, ‘beb50511de04af606e7086b30c66462d’),
(‘xlf’, xlfFile)]

response, status, code, message, content = api.callMethod(“LayoutRegionMediaEdit”, params)
print status

There’s not enough information there to help you. We’ve no idea what is in layout 8, whether there’s a region with that ID or a media item with that ID, nor what xlfFile variable contains.