Fixed #22236 -- Removed inappropriate usage of signals

from django.apps import apps

from django.apps.config import MODELS_MODULE_NAME

import django.db.models.manager  # NOQA: Imported to register signal handler.

from django.conf import settings

from django.core import checks

from django.core.exceptions import (ObjectDoesNotExist,

    MultipleObjectsReturned, FieldError, ValidationError, NON_FIELD_ERRORS)

from django.db import (router, transaction, DatabaseError,

    DEFAULT_DB_ALIAS)

from django.db.models.deletion import Collector

from django.db.models.fields import AutoField, FieldDoesNotExist

from django.db.models.fields.related import (ForeignObjectRel, ManyToOneRel,

    OneToOneField, add_lazy_relation)

from django.db import (router, transaction, DatabaseError,

    DEFAULT_DB_ALIAS)

from django.db.models.manager import ensure_default_manager

from django.db.models.options import Options

from django.db.models.query import Q

from django.db.models.query_utils import DeferredAttribute, deferred_class_factory

from django.db.models.deletion import Collector

from django.db.models.options import Options

from django.db.models import signals

from django.utils import six

from django.utils.deprecation import RemovedInDjango19Warning

            cls.get_absolute_url = update_wrapper(curry(get_absolute_url, opts, cls.get_absolute_url),

                                                  cls.get_absolute_url)

        ensure_default_manager(cls)

        signals.class_prepared.send(sender=cls)

from django.db import router

from django.db.models.query import QuerySet

from django.db.models import signals

from django.db.models.fields import FieldDoesNotExist

from django.utils import six

from django.utils.encoding import python_2_unicode_compatible

def ensure_default_manager(sender, **kwargs):

def ensure_default_manager(cls):

    """

    Ensures that a Model subclass contains a default manager  and sets the

    _default_manager attribute on the class. Also sets up the _base_manager

    points to a plain Manager instance (which could be the same as

    _default_manager if it's not a subclass of Manager).

    """

    cls = sender

    if cls._meta.abstract:

        setattr(cls, 'objects', AbstractManagerDescriptor(cls))

        return

                    return

            raise AssertionError("Should never get here. Please report a bug, including your model and model manager setup.")

signals.class_prepared.connect(ensure_default_manager)

@python_2_unicode_compatible

class BaseManager(object):