Steps to replicate the issue (include links if applicable):

• Create a new redirect to an already existing redirect.

What happens?:

MediaWiki allows you to make a double redirect like this, no worries. On WMF wikis, a bot comes along and fixes the mess, but not all wikis have these bots.

What should have happened instead?:

An error message should appear, similar to MediaWiki:Selfredirect, but specifically for this problem (creating a double redirect). This should advise the user to change the redirect target to the target of the second redirect.

Note that there is a check for self-redirects at this point. This is analogous.

Software version (skip for WMF-hosted wikis like Wikipedia): 1.35

Other information (browser name/version, screenshots, etc.):