Default to Celery Task model when backend model does not exist (#14612)
Default to Celery Task model when backend model does not exist (#14612)

closes https://github.com/apache/airflow/issues/14586

We add this feature in https://github.com/apache/airflow/pull/12336
but looks like for some users this attribute does not exist.

I am not sure if they are using a different Celery DB Backend or not
but even Celery > 5 contains this attribute
(https://github.com/celery/celery/blob/v5.0.5/celery/backends/database/__init__.py#L66)

and even Celery 4 but this commits use the Celery Task model when an attribute
error occurs

sekikn/incubator-airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,apache/airflow,apache/incubator-airflow,bolkedebruin/airflow,apache/airflow,sekikn/incubator-airflow,danielvdende/incubator-airflow,sekikn/incubator-airflow,apache/incubator-airflow,danielvdende/incubator-airflow,bolkedebruin/airflow,dhuang/incubator-airflow,lyft/incubator-airflow,dhuang/incubator-airflow,apache/incubator-airflow,mistercrunch/airflow,cfei18/incubator-airflow,mistercrunch/airflow,bolkedebruin/airflow,cfei18/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,dhuang/incubator-airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,lyft/incubator-airflow,lyft/incubator-airflow,apache/airflow,apache/airflow,sekikn/incubator-airflow,mistercrunch/airflow,Acehaidrey/incubator-airflow,bolkedebruin/airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,apache/incubator-airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,mistercrunch/airflow,bolkedebruin/airflow,apache/airflow,nathanielvarona/airflow,nathanielvarona/airflow,dhuang/incubator-airflow,cfei18/incubator-airflow,nathanielvarona/airflow,lyft/incubator-airflow,apache/airflow