Add task to process a DVLA response file:

* Currently we do nothing with the parsed response. We will
* update the status of the notifications in a separate PR

app/dao/notifications_dao.py

@@ -27,7 +27,8 @@ from app.models import (
     NOTIFICATION_PERMANENT_FAILURE,
     KEY_TYPE_NORMAL, KEY_TYPE_TEST,
     LETTER_TYPE,
-    NOTIFICATION_SENT)
+    NOTIFICATION_SENT
+)
 
 from app.dao.dao_utils import transactional
 from app.statsd_decorators import statsd