Improve guidance to users telling them what to do on import timeout (#18478)
Improve guidance to users telling them what to do on import timeout (#18478)

* Improve guidance to users telling them what to do on import timeout

The message about import timeut does not explain an average user
what the root cause is. The updated one links to the docuementation
on how to reduce tpo-level Python code overhead and reduce
complexity of their DAGs.

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