*line* should be bytes

def output(self, kind, line):
        "*line* should be bytes"
        self.destination.write(b''.join([
            self._cyan,
            b't=%07d' % (time.time() - self._t0),
            self._reset,
            self._kind_prefixes[kind],
            self.markers[kind],
            line,
            self._reset,
        ]))
        self.destination.flush()