[Piuparts-reports] problem with piuparts-slave detected

[piuparts slave]

Either a test is running for a very long time (more than 90 minutes),
or piuparts-slave hangs or is not running at all or wasn't started with
~piupartss/bin/slave_run - please investigate and take appropriate measures!

  File "/srv/piuparts.debian.org/share/piuparts/piuparts-slave", line 416, in _connect_to_master
    self._slave.connect_to_master()
  File "/srv/piuparts.debian.org/share/piuparts/piuparts-slave", line 228, in connect_to_master
    self._initial_connect()
  File "/srv/piuparts.debian.org/share/piuparts/piuparts-slave", line 244, in _initial_connect
    line = self._readline()
  File "/srv/piuparts.debian.org/share/piuparts/piuparts-slave", line 192, in _readline
    logging.debug("<< " + line.rstrip())
TypeError: can only concatenate str (not "bytes") to str
piupartss at piu-slave-ubc-01:/srv/piuparts.debian.org/slave/1$ 
piupartss at piu-slave-ubc-01:/srv/piuparts.debian.org/slave/1$ exit