message: fix error message when running toco from python3.
  Otherwize it's still bytes, so the exception reports the entire console output on a single line, making it unreadable.
diff: @@ -52,6 +52,16 @@ else:
  if _toco_from_proto_bin and not _os.path.exists(_toco_from_proto_bin):
  _toco_from_proto_bin = "toco_from_protos"
  +def _try_convert_to_unicode(output):
  + if output is None:
  + return u""
  +
  + if isinstance(output, bytes):
  + try:
  + return output.decode()
  + except UnicodeDecodeError:
  + pass
  + return output
  class ConverterMode(enum.Enum):
  """Enum class defining the converters available to generate TFLite models.
  @@ -145,6 +155,8 @@ def toco_convert_protos(model_flags_str, toco_flags_str, input_data_str):
  with open(output_filename, "rb") as fp:
  return fp.read()
  else:
  + stdout = _try_convert_to_unicode(stdout)
  + stderr = _try_convert_to_unicode(stderr)
  raise RuntimeError(
  "TOCO failed see console for info.\n%s\n%s\n" % (stdout, stderr))
  finally:
  