Purge duplicates from TaskFail prior to 2.3 upgrade (#22769)
Purge duplicates from TaskFail prior to 2.3 upgrade (#22769)

We're adding a PK to TaskFail in 2.3 so we wanted to check and move dupes out of the table prior to upgrade.  Why do we do it in pre-upgrade check instead of in the migration? (1) historical reasons, we initially only "checked" and failed with this type of thing but then realized we needed to actualy move the rows out but did want to move the code (2) will take a little more thought concering how to implement with `--sql-mode` given that we don't know until we run the migrations whether those `_airflow_moved` tables will need to be created and if we create them unnecessarily then many users will get unneeded warnings in the web UI (we warn and tell users to deal with these tables if they are created).
danielvdende/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,nathanielvarona/airflow,cfei18/incubator-airflow,apache/airflow,apache/airflow,apache/airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,apache/airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,lyft/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,lyft/incubator-airflow,nathanielvarona/airflow