[EWT-499] Airflow Upgrade to 1.10.12 [CP] from 1.10.4+twtr : 9b58c88

*Cherry-Pick contains [CP][EWT-302]Patch Pool.DEFAULT_POOL_NAME in BaseOperator (apache#8587) (twitter-forks#49)

Open source commit id: b37ce29

Co-authored-by: Vishesh Jain <visheshj@twitter.com>

UPDATING.md

@@ -214,6 +214,18 @@ The following metrics are deprecated and won't be emitted in Airflow 2.0:
 
 No breaking changes.
 
+## CP
+
+### Ability to patch Pool.DEFAULT_POOL_NAME in BaseOperator
+It was not possible to patch pool in BaseOperator as the signature sets the default value of pool
+as Pool.DEFAULT_POOL_NAME.
+While using subdagoperator in unittest(without initializing the sqlite db), it was throwing the
+following error:
+```
+sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such table: slot_pool.
+```
+Fix for this, https://github.com/apache/airflow/pull/8587
+
 ## Airflow 1.10.4
 
 ### Export MySQL timestamps as UTC

airflow/models/baseoperator.py

@@ -309,7 +309,7 @@ def __init__(
         priority_weight=1,  # type: int
         weight_rule=WeightRule.DOWNSTREAM,  # type: str
         queue=conf.get('celery', 'default_queue'),  # type: str
-        pool=Pool.DEFAULT_POOL_NAME,  # type: str
+        pool=None,  # type: str
         pool_slots=1,  # type: int
         sla=None,  # type: Optional[timedelta]
         execution_timeout=None,  # type: Optional[timedelta]
@@ -379,7 +379,7 @@ def __init__(
         self._schedule_interval = schedule_interval
         self.retries = retries
         self.queue = queue
-        self.pool = pool
+        self.pool = Pool.DEFAULT_POOL_NAME if pool is None else pool
         self.pool_slots = pool_slots
         if self.pool_slots < 1:
             raise AirflowException("pool slots for %s in dag %s cannot be less than 1"