Add Notifications of build failures (#22552)
Add Notifications of build failures (#22552)

There is new feature to receive notifications about build failures
for git repos. It is supposed to only send info about changed
status -> failed/succeeded or succeeded-> failed transition.

Trying it out.
Acehaidrey/incubator-airflow,nathanielvarona/airflow,lyft/incubator-airflow,lyft/incubator-airflow,apache/airflow,apache/airflow,lyft/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,apache/airflow,cfei18/incubator-airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,apache/airflow,danielvdende/incubator-airflow,lyft/incubator-airflow,apache/airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,cfei18/incubator-airflow,apache/airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,cfei18/incubator-airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,Acehaidrey/incubator-airflow