message: Fix a pytype error in system_info_lib.
  This allows us to turn on PY3 for t2t_trainer_xla.
diff: @@ -81,7 +81,7 @@ def gather_cpu_info():
  # Gather num_cores_allowed
  try:
  with gfile.GFile('/proc/self/status', 'rb') as fh:
  - nc = re.search(r'(?m)^Cpus_allowed:\s*(.*)$', fh.read())
  + nc = re.search(r'(?m)^Cpus_allowed:\s*(.*)$', fh.read().decode('utf-8'))
  if nc: # e.g. 'ff' => 8, 'fff' => 12
  cpu_info.num_cores_allowed = (
  bin(int(nc.group(1).replace(',', ''), 16)).count('1'))
  