Add updated history count to dao_update_notifications_by_reference

For returned letter updates most notifications won't exist in the
notifications table, so in order to find out whether the reference
matches any known letters we need to check the count of updated
history records.

app/celery/letters_pdf_tasks.py

@@ -288,7 +288,7 @@ def update_letter_pdf_status(reference, status):
         update_dict={
             'status': status,
             'updated_at': datetime.utcnow()
-        })
+        })[0]
 
 
 def replay_letters_in_error(filename=None):

app/celery/tasks.py

@@ -339,7 +339,7 @@ def update_letter_notifications_to_sent_to_dvla(self, notification_references):
     # This task will be called by the FTP app to update notifications as sent to DVLA
     provider = get_current_provider(LETTER_TYPE)
 
-    updated_count = dao_update_notifications_by_reference(
+    updated_count, _ = dao_update_notifications_by_reference(
         notification_references,
         {
             'status': NOTIFICATION_SENDING,
@@ -357,7 +357,7 @@ def update_letter_notifications_to_sent_to_dvla(self, notification_references):
 def update_letter_notifications_to_error(self, notification_references):
     # This task will be called by the FTP app to update notifications as sent to DVLA
 
-    updated_count = dao_update_notifications_by_reference(
+    updated_count, _ = dao_update_notifications_by_reference(
         notification_references,
         {
             'status': NOTIFICATION_TECHNICAL_FAILURE,
@@ -465,7 +465,7 @@ def update_letter_notification(filename, temporary_failures, update):
         status = NOTIFICATION_TEMPORARY_FAILURE
         temporary_failures.append(update.reference)
 
-    updated_count = dao_update_notifications_by_reference(
+    updated_count, _ = dao_update_notifications_by_reference(
         references=[update.reference],
         update_dict={"status": status,
                      "billable_units": update.page_count,

app/dao/notifications_dao.py

@@ -465,14 +465,14 @@ def dao_update_notifications_by_reference(references, update_dict):
         synchronize_session=False
     )
 
-    NotificationHistory.query.filter(
+    updated_history_count = NotificationHistory.query.filter(
         NotificationHistory.reference.in_(references)
     ).update(
         update_dict,
         synchronize_session=False
     )
 
-    return updated_count
+    return updated_count, updated_history_count
 
 
 @statsd(namespace="dao")