code: def system(self, cmd, fake_code=False):
          
          try:
              if self.options.dry_run:
                  def fake_system(cmd):
                      self.print_message(cmd)
                      return fake_code
  
                  return fake_system(cmd)
          except AttributeError:
              self.logger.warnning("fake mode enabled,"
                                   "but you don't set '--dry-run' option "
                                   "in your argparser options")
              pass
  
          return os.system(cmd)
docs: a built-in wrapper make dry-run easier.
          you should use this instead use `os.system`
  
          .. note::
  
              to use it,you need add '--dry-run' option in
              your argparser options
  
  
          :param str cmd: command to execute
          :param bool fake_code: only display command
              when is True,default is False
          :return: