Serializing Django's ErrorList results in invalid bytes

[LilyFirefly]

I've created a minimal example.

# msgpack_errorlist.tests
from unittest import TestCase

import msgpack
from django.forms.utils import ErrorList


class MsgpackTestCase(TestCase):
    def test_errorlist(self):
        data = ErrorList("T")

        raw = msgpack.packb(data)

        msgpack.unpackb(raw)

msgpack_errorlist$ python manage.py test
Found 1 test(s).
System check identified no issues (0 silenced).
E
======================================================================
ERROR: test_errorlist (msgpack_errorlist.tests.MsgpackTestCase.test_errorlist)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/lily/work/kloppindustries/msgpack_errorlist/msgpack_errorlist/tests.py", line 13, in test_errorlist
    msgpack.unpackb(raw)
  File "msgpack/_unpacker.pyx", line 201, in msgpack._cmsgpack.unpackb
msgpack.exceptions.ExtraData: unpack(b) received extra data.

----------------------------------------------------------------------
Ran 1 test in 0.000s

FAILED (errors=1)

The invalid msgpack bytes are: \x90\xa1T.

My unproven suspicion is that this is something to do with ErrorList subclassing list.

[LilyFoote]

Ah! I just discovered the strict_types flag! Using that solves this for me.