Django Celery django.db.utils.OperationalError

Question

Hi I'm having a really strange problem with celery. I have a model like this

class MyUser(models.model):
    email = models.CharField(max_length=255, unique=True, blank=False, null=False)
    .....
    user_code = models.PositiveIntegerField(default=get_user_code, unique=True, blank=False, null=False)


def get_random_num():
    return random.randint(10000, 999999)


def get_user_code():
    # Check if some user with this code already exists
    code = get_random_num()
    while MyUser.objects.filter(user_code=code).exists():
        code = get_random_num()
    return code

So django is not complaining on this, but for some reason when I start celery I have errors like this:

django.db.utils.OperationalError: could not receive data from server: Bad file descriptor

Django schedule tasks will not run, other celery tasks run just fine (example: sending emails).

So django is not complaining on this but Celery does.

If I just remove this lines of code, celery is not showing any errors.

while MyUser.objects.filter(user_code=code).exists():
    code = get_random_num()

Why is Celery complaining on this? Did someone already faced this issue? Is there some clean way to avoid this?