debug/spoof: cannot instantiate io_line_follower_t

[tmplt]

$ ./lcm-debug-spoof-message.py IO_LINE_FOLLOWER 0 0
Traceback (most recent call last):
  File "./lcm-debug-spoof-message.py", line 52, in <module>
    lcm.LCM().publish(channel, msg.encode())
  File "/nix/store/r4d96703p1cd1s7dzi3sx47khllk07qg-lcm-python/lib/python3.8/site-packages/robot/io_line_follower_t.py", line 26, in encode
    self._encode_one(buf)
  File "/nix/store/r4d96703p1cd1s7dzi3sx47khllk07qg-lcm-python/lib/python3.8/site-packages/robot/io_line_follower_t.py", line 30, in _encode_one
    buf.write(struct.pack('>4b', *self.detected[:4]))
struct.error: pack expected 4 items for packing (got 1)