message: tests: Replace usage of tostring() with tobytes()
  tostring() is deprecated as of python 3.7 and results in stderr output
  causing tests to fail
diff: @@ -107,7 +107,7 @@ def all_interfaces():
  max_possible *= 2
  else:
  break
  - namestr = names.tostring()
  + namestr = names.tobytes()
  return [(namestr[i:i+16].split(b'\0', 1)[0],
  socket.inet_ntoa(namestr[i+20:i+24]))
  for i in range(0, outbytes, struct_size)]
  