Now that we have discovered that the catch all Exception handler doesn't work, I've created a custom exception (SendNotificationQueueError) that handles this case and an error handler for it.

Talked these through with @becca as an approach.

tests/app/notifications/test_process_notification.py

@@ -5,6 +5,7 @@ from boto3.exceptions import Boto3Error
 from sqlalchemy.exc import SQLAlchemyError
 
 from app.models import Template, Notification, NotificationHistory
+from app.notifications import SendNotificationToQueueError
 from app.notifications.process_notifications import (create_content_for_notification,
                                                      persist_notification, send_notification_to_queue)
 from app.v2.errors import BadRequestError
@@ -108,7 +109,7 @@ def test_send_notification_to_queue(notify_db, notify_db_session,
 
 def test_send_notification_to_queue_throws_exception_deletes_notification(sample_notification, mocker):
     mocked = mocker.patch('app.celery.provider_tasks.deliver_sms.apply_async', side_effect=Boto3Error("EXPECTED"))
-    with pytest.raises(Boto3Error):
+    with pytest.raises(SendNotificationToQueueError):
         send_notification_to_queue(sample_notification, False)
         mocked.assert_called_once_with([(str(sample_notification.id))], queue='send-sms')