python3 AttributeError: 'NoneType' object has no attribute 'split'

 from wsgiref.simple_server import make_server

 def RunServer(environ, start_response):
     start_response('200 ok',[('Content-Type','text/html')])
     return '<h1>Hello world</h1>'

 if __name__ == '__main__':
     httpd = make_server('127.0.0.1',9000,RunServer)
     print('servering HTTP on port 9000')
     httpd.serve_forever()

Code

运行时报错：

self.status.split(' ',1)[0], self.bytes_sent
AttributeError: 'NoneType' object has no attribute 'split'

解决办法如下：

return ['<h1>Hello world</h1>'.encode('utf-8'),]