URL of CreateView doesn't work

[KenWhitesell]

@TiimeIrreVaali

    path('<slug:subforum_slug>/<slug:topic_slug>/', ShowTopic.as_view(), name='topic'),
    path('<slug:subforum_slug>/add_topic/', AddTopic.as_view(), name="add_topic"),

The issue here is that URLs are searched sequentially. The first pattern that a URL matches will be the one that is used.

Since the literal string “add_topic” would be a valid slug, the url http://127.0.0.1:8000/forum/production/add_topic/ is going to match the first pattern, and end up calling the view ShowTopic as shown in your error message.