From @leao-nardo :
Old links (before Django update migration) are not valid anymore. This is not good as these links are widespread over the Internet and we don't want them to be broken.

We need to create a new view that redirects URLs with the old format to the new one. For example:
Old URL: http://dojopuzzles.com/problemas/exibe/fizzbuzz
New URL: https://dojopuzzles.com/problems/fizzbuzz

This can be acomplished adding a new URL route that identify the slug and redirects to the right URL:
Old URL pattern: http://dojopuzzles.com/problemas/exibe/<slug>
New URL pattern: https://dojopuzzles.com/problems/<slug>

slug is the same in old a new versions, so if you get the slug from old URL, you can use in new URL as well.

hey, can I work on this?

Sure you can!

seems like it's already done so i'm closing, right ?