When calling the Satellite 5 API method activationkey.listActivatedSystems it throws the error "xml.parsers.expat.ExpatError: XML or text declaration not at start of entity"

Issue

• When calling the Satellite 5 API method activationkey.listActivatedSystems it throws the error xml.parsers.expat.ExpatError: XML or text declaration not at start of entity

Traceback (most recent call last):
  File "./list_systems.py", line 15, in <module>
    systems = client.activationkey.listActivatedSystems(key, ACTIVATIONKEY)
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1199, in __call__
    return self.__send(self.__name, args)
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1489, in __request
    verbose=self.__verbose
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1253, in request
    return self._parse_response(h.getfile(), sock)
  File "/usr/lib64/python2.6/xmlrpclib.py", line 1387, in _parse_response
    p.feed(response)
  File "/usr/lib64/python2.6/xmlrpclib.py", line 601, in feed
    self._parser.Parse(data, 0)
xml.parsers.expat.ExpatError: XML or text declaration not at start of entity: line 1, column 4795