MultipleObjectsReturned at /rants/first-rant/ get() returned more than one Rant -- it returned 2

I'm getting the error because I have two first-rant slug's on the database. I expected this to come. I have a solution in mind to add random numbers at the end of the url. Can anyone help me implement this using the RandomCharField of https://django-extensions.readthedocs.io/en/latest/field_extensions.html.

Here are my models: