In this lesson, you’re going to look at how to build routes. In the previous lesson, you tried a URL that doesn’t exist and got an error message that told you to check portfolio.url.
When you check that file, you can see all of the URL patterns that exist there. If you try to go to /projects, then you’ll see that it isn’t registered anywhere, so Django doesn’t know what to do with it. Fortunately, Django provides a lot of useful information in the comment at the top of that file.

Pygator on Oct. 12, 2019
I get this mistake when rerunning the server after adding to the
urlpatterns: