Django and Celery, AppRegistryNotReady: Apps aren't loaded yet.

django版本升级导致celery启动报错，主要原因：django升级后的版本和celery版本不兼容。
我的案例：

# 升级前
django==1.8.11
celery==3.1.18
django-celery==3.2.1
# 升级后
django==1.11.24
celery==3.1.25
django-celery==3.2.2

报错信息：

[2019-12-20 14:44:58,741: ERROR/Worker-1] Process Worker-1
Traceback (most recent call last):
  File "C:\Python3.6\lib\site-packages\kombu\utils\__init__.py", line 323, in __get__
    return obj.__dict__[self.__name__]
KeyError: 'backend'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Python3.6\lib\site-packages\billiard\process.py", line 292, in _bootstrap
    self.run()
  File "C:\Python3.6\lib\site-packages\billiard\pool.py", line 292, in run
    self.after_fork()
  File "C:\Python3.6\lib\site-packages\billiard\pool.py", line 395, in after_fork
    self.initializer(