docs: def _handle_stdout(self, ioloop, f, count=-1):
          """ because anonymous pipes in windows can be blocked, we need to pay attention
          on how much we read
          """
          output = non_blocking_read(self._popen.stdout, count)
          if not output:
              self._popen.stdout.close()
              self._popen.stdout = None
          else:
              self._output.write(output)
              self._register_stdout(ioloop)