text: from twisted.test import proto_helpers
  
  class StringTransport:
  
      def write(self, data):
          if isinstance(data, str): # no, really, I mean it
              raise TypeError("Data must not be unicode")
          self.io.write(data)
  
  def install():
      proto_helpers.StringTransport.__dict__['write'] = StringTransport.__dict__['write']
  