[AIRFLOW-5280] conn: Remove aws_default's default region name

UPDATING.md

@@ -40,6 +40,14 @@ assists users migrating to a new version.
 
 ## Airflow Master
 
+### Changes to `aws_default` Connection's default region
+
+The region of Airflow's default connection to AWS (`aws_default`) has
+previously been set to `us-east-1` during installation.
+
+The region now needs to be set manually either in the connection screens in
+Airflow, or via the `AWS_DEFAULT_REGION` environment variable.
+
 ### Changes to import paths and names of GCP operators and hooks
 
 According to [AIP-21](https://cwiki.apache.org/confluence/display/AIRFLOW/AIP-21%3A+Changes+in+import+paths) 

airflow/utils/db.py

@@ -194,8 +194,7 @@ def initdb():
             extra='{"path": "/"}'))
     merge_conn(
         Connection(
-            conn_id='aws_default', conn_type='aws',
-            extra='{"region_name": "us-east-1"}'))
+            conn_id='aws_default', conn_type='aws'))
     merge_conn(
         Connection(
             conn_id='spark_default', conn_type='spark',

docs/howto/connection/aws.rst

@@ -35,6 +35,8 @@ Default Connection IDs
 
 The default connection ID is ``aws_default``.
 
+.. note:: Previously, the ``aws_default`` connection had the "extras" field set to ``{"region_name": "us-east-1"}`` on install. This means that by default the ``aws_default`` connection used the ``us-east-1`` region. This is no longer the case and the region needs to be set manually, either in the connection screens in Airflow, or via the ``AWS_DEFAULT_REGION`` environment variable.
+
 Configuring the Connection
 --------------------------
 

run-tests

@@ -47,6 +47,9 @@ export AIRFLOW__CORE__UNIT_TEST_MODE=True
 # add test/test_utils to PYTHONPATH TODO: Do we need that ??? Looks fishy.
 export PYTHONPATH=${PYTHONPATH:=}:${AIRFLOW_SOURCES}/tests/test_utils
 
+# make sure the default AWS_REGION is set
+export AWS_DEFAULT_REGION=${AWS_DEFAULT_REGION:='us-east-1'}
+
 echo Airflow home: "${AIRFLOW_HOME}"
 echo Airflow root: "${AIRFLOW_SOURCES}"
 echo Home of the user: "${HOME}"

scripts/ci/in_container/entrypoint_ci.sh

@@ -122,6 +122,9 @@ export PATH=${PATH}:${AIRFLOW_SOURCES}
 
 export AIRFLOW__CORE__UNIT_TEST_MODE=True
 
+# Make sure all AWS API calls default to the us-east-1 region
+export AWS_DEFAULT_REGION=${AWS_DEFAULT_REGION:='us-east-1'}
+
 # Fix codecov build path
 # TODO: Check this - this should be made travis-independent
 if [[ ! -h /home/travis/build/apache/airflow ]]; then