serializers.py

import pickle
import six
from django_redis.serializers.pickle import PickleSerializer

def compat_pickle_loads(value, **kwargs):
    if six.PY2:
        return _py2_pickle_loads(value)
    return _py3_pickle_loads(value, **kwargs)


def _py2_pickle_loads(value):
    return pickle.loads(value)


def _py3_pickle_loads(value, **kwargs):
    try:
        return pickle.loads(value, **kwargs)
    except UnicodeDecodeError:
        return pickle.loads(value, encoding="latin1", **kwargs)

class SixPickleSerializer(PickleSerializer):
    # for https://github.com/niwinz/django-redis
    def loads(self, value):
        return compat_pickle_loads(value)

settings.py

CACHES = {
    "default": {
        "LOCATION": [
            "redis://{0}:{1}/1".format(self._REDIS_HOST, self._REDIS_PORT),
            "redis://{0}:{1}/1".format(self._REDIS_HOST_READONLY, self._REDIS_PORT),
        ],
        "OPTIONS": {
            "PARSER_CLASS": "redis.connection.HiredisParser",
            "PICKLE_VERSION": 2,  # compat with py2 and py3
            "SERIALIZER": "core.serializers.SixPickleSerializer",
            "REDIS_CLIENT_KWARGS": {
                "health_check_interval": 30  # https://github.com/andymccurdy/redis-py/issues/1186
            },
        },
    }
}

test.py

from core.serializers import compat_pickle_loads
...

class TestPickleCompat(TestCase):
    def test_compat(self):
        value = b"\x80\x02}q\x01U\x0e_in_stock_dateq\x02cdatetime\ndate\nq\x03U\x04\x07\xe4\x01\t\x85Rq\x04s."
        self.assertEqual(compat_pickle_loads(value), {"_in_stock_date": datetime.date(2020, 1, 9)})