Add task to remove transformed dvla files:

* Runs at 4:40am
* Remove files older than 7 days and only two day's worth

app/celery/scheduled_tasks.py

@@ -24,6 +24,7 @@ from app.dao.provider_details_dao import (
     dao_toggle_sms_provider
 )
 from app.dao.users_dao import delete_codes_older_created_more_than_a_day_ago
+from app.models import LETTER_TYPE
 from app.notifications.process_notifications import send_notification_to_queue
 from app.statsd_decorators import statsd
 from app.celery.tasks import process_job
@@ -245,3 +246,12 @@ def delete_inbound_sms_older_than_seven_days():
     except SQLAlchemyError as e:
         current_app.logger.exception("Failed to delete inbound sms notifications")
         raise
+
+
+@notify_celery.task(name="remove_transformed_dvla_files")
+@statsd(namespace="tasks")
+def remove_transformed_dvla_files():
+    jobs = dao_get_jobs_older_than_limited_by(job_types=[LETTER_TYPE])
+    for job in jobs:
+        s3.remove_transformed_dvla_file(job.id)
+        current_app.logger.info("Transformed dvla file for job {} has been removed from s3.".format(job.id))