Add the required migration for time machine tag lifetimes.

util/backfill_user_uuids.py

@@ -15,7 +15,7 @@ def backfill_user_uuids():
   # Check to see if any users are missing uuids.
   has_missing_uuids = True
   try:
-    User.select().where(User.uuid >> None).get()
+    User.select(User.id).where(User.uuid >> None).get()
   except User.DoesNotExist:
     has_missing_uuids = False
 
@@ -39,9 +39,9 @@ def backfill_user_uuids():
     for user_id in batch_user_ids:
       with app.config['DB_TRANSACTION_FACTORY'](db):
         try:
-          user = User.get(User.id == user_id)
+          user = User.select(User.id, User.uuid).where(User.id == user_id).get()
           user.uuid = str(uuid.uuid4())
-          user.save()
+          user.save(only=[User.uuid])
         except User.DoesNotExist:
           pass