Don't use str.format() when logging.

The correct way to log is to use %-formatting, and pass the format args to
the logging function. This prevents the string from being formatted at all
when the log item isn't logged anywhere (in this case, when the log level
is WARNING or higher).

pillar/cli/operations.py

@@ -132,7 +132,7 @@ def index_users_rebuild():
 
     users_index = current_app.algolia_index_users
 
-    log.info('Dropping index: {}'.format(users_index))
+    log.info('Dropping existing index: %s', users_index)
     users_index.clear_index()
     index_users_update_settings()