puts a warning message if there is a leap in indentation -- e.g. a level 1 item followed by a level 3 item skipping a level 2. This may flood the warning log and there is no way to stop it other than removing the indentation leap.
Meanwhile, unless you look into the warning log, you don't notice that's happening partly because an indentation leap is silently corrected. Given that, the warning message is better to be a debug message, which you turn it on by setting DEBUG on.