Remove deprecated 'bql' parameter (GoogleCloudPlatform#2179)

* Remove deprecated migration scripts

* Comment out unused imports to pass linter

* Remove commented out imports

* Remove deprecated migration scripts

* Add readme pointing to env upgrade docs

* Replace deprecated 'bql' with 'sql' in BQ DAGs

* Revert copyright year to creation year, not edit

Author: leahecole

composer/workflows/bq_notify.py

@@ -99,7 +99,7 @@
     # Query recent StackOverflow questions.
     bq_recent_questions_query = bigquery_operator.BigQueryOperator(
         task_id='bq_recent_questions_query',
-        bql="""
+        sql="""
         SELECT owner_display_name, title, view_count
         FROM `bigquery-public-data.stackoverflow.posts_questions`
         WHERE creation_date < CAST('{max_date}' AS TIMESTAMP)
@@ -121,7 +121,7 @@
     # Perform most popular question query.
     bq_most_popular_query = bigquery_operator.BigQueryOperator(
         task_id='bq_most_popular_question_query',
-        bql="""
+        sql="""
         SELECT title, view_count
         FROM `{table}`
         ORDER BY view_count DESC

composer/workflows/connections.py

@@ -40,19 +40,19 @@
     # [START composer_connections_default]
     task_default = bigquery_operator.BigQueryOperator(
         task_id='task_default_connection',
-        bql='SELECT 1', use_legacy_sql=False)
+        sql='SELECT 1', use_legacy_sql=False)
     # [END composer_connections_default]
     # [START composer_connections_explicit]
     task_explicit = bigquery_operator.BigQueryOperator(
         task_id='task_explicit_connection',
-        bql='SELECT 1', use_legacy_sql=False,
+        sql='SELECT 1', use_legacy_sql=False,
         # Composer creates a 'google_cloud_default' connection by default.
         bigquery_conn_id='google_cloud_default')
     # [END composer_connections_explicit]
     # [START composer_connections_custom]
     task_custom = bigquery_operator.BigQueryOperator(
         task_id='task_custom_connection',
-        bql='SELECT 1', use_legacy_sql=False,
+        sql='SELECT 1', use_legacy_sql=False,
         # Set a connection ID to use a connection that you have created.
         bigquery_conn_id='my_gcp_connection')
     # [END composer_connections_custom]