A broken 404 template in Django can swallow your backtraces

Note I wrote this post as an exercise during a meeting of IndieWebClub Bangalore. I recently migrated this website from Astro to Wagtail. The reason why I did it is a story for another day. In this post, I want to talk about a bug that took me far too long to figure out.In his (verifiably incorrect) post about making chai, Abhigyan linked to my own (verifiably correct) post on the topic. While linking to my post, he accidentally omitted the trailing slash from the URL.This shouldn't have been a problem. By default, Django automatically redirects a URL without a trailing slash to the same URL with the trailing slash appended, provided the original URL returns a 404. For example, if you try to access the following URL on my website:https://ankursethi.com/about Django automatically performs a 301 redirect to:https://ankursethi.com/about/ This is the default behavior, controlled by the APPEND_SLASH setting. However, when Abhigyan linked to my (verifiably correct) post about making chai,…