Read the data stream until a given separator is found (default \n)

        :param sep: Separator to read until. Must by of the bytes type (str in python 2,
            bytes in python 3)
        :return: The str of the data read until sep

def read_line(self, sep=six.b('\n')):
        """Read the data stream until a given separator is found (default \n)

        :param sep: Separator to read until. Must by of the bytes type (str in python 2,
            bytes in python 3)
        :return: The str of the data read until sep
        """
        start = 0
        while not self._stream.closed:
            loc = self._buffer.find(sep, start)
            if loc >= 0:
                return self._pop(loc + len(sep))
            else:
                start = len(self._buffer)
            self._buffer += self._stream.read(self._chunk_size)
        return six.b('')