Xmlrpclib调用自定义方法报错

[gmasss]

自定义的方法及测试代码如下：

class res_users(osv.osv):
    _name = 'res.users'
    _inherit = 'res.users'
    _columns = {
            'vocation_days':fields.float(u'假期总天数',size=44,required=True),
            }
    def change_vocation_days(self, cr, uid, context=None):
        print('ni hao')
   
res_users()


if name == "main":
    import xmlrpclib
    sock = xmlrpclib.ServerProxy('http://localhost:8069/xmlrpc/object',allow_none=True)
    uid=1
    pwd='123'
    dbname="aaa"
    sock.execute(dbname,uid,pwd,'res.users','change_vocation_days')
 


报错信息如下：
Traceback (most recent call last):
  File "F:\GreenOpenERP-7.0-20131004-231118\openerp\addons\qingjd\qingjd.py", line 47, in <module>
    name=sock.execute(dbname,uid,pwd,'res.users','change_vocation_days')
  File "F:\GreenOpenERP-7.0-20131004-231118\python\lib\xmlrpclib.py", line 1224, in call
    return self.__send(self.__name, args)
  File "F:\GreenOpenERP-7.0-20131004-231118\python\lib\xmlrpclib.py", line 1578, in __request
    verbose=self.__verbose
  File "F:\GreenOpenERP-7.0-20131004-231118\python\lib\xmlrpclib.py", line 1264, in request
    return self.single_request(host, handler, request_body, verbose)
  File "F:\GreenOpenERP-7.0-20131004-231118\python\lib\xmlrpclib.py", line 1297, in single_request
    return self.parse_response(response)
  File "F:\GreenOpenERP-7.0-20131004-231118\python\lib\xmlrpclib.py", line 1473, in parse_response
    return u.close()
  File "F:\GreenOpenERP-7.0-20131004-231118\python\lib\xmlrpclib.py", line 793, in close
    raise Fault(**self._stack[0])
xmlrpclib.Fault: <Fault cannot marshal None unless allow_none is enabled: 'Traceback (most recent call last):\n  File "F:\GreenOpenERP-7.0-20131004-231118\openerp\service\wsgi_server.py", line 83, in xmlrpc_return\n    response = xmlrpclib.dumps((result,), methodresponse=1, allow_none=False, encoding=None)\n  File "F:\GreenOpenERP-7.0-20131004-231118\python\lib\xmlrpclib.py", line 1085, in dumps\n    data = m.dumps(params)\n  File "F:\GreenOpenERP-7.0-20131004-231118\python\lib\xmlrpclib.py", line 632, in dumps\n    dump(v, write)\n  File "F:\GreenOpenERP-7.0-20131004-231118\python\lib\xmlrpclib.py", line 654, in __dump\n    f(self, value, write)\n  File "F:\GreenOpenERP-7.0-20131004-231118\python\lib\xmlrpclib.py", line 658, in dump_nil\n    raise TypeError, "cannot marshal None unless allow_none is enabled"\nTypeError: cannot marshal None unless allow_none is enabled\n'>

请各位不吝赐教。