@kennethlove My most common usage for this mixin is for login and registration view. If users are already logged in I would suppose to redirect them to the same page to which they are redirected after log in / registration. 

I would appreciate some default value - not raising exception if ``authenticated_redirect_url`` is missing. Imho even E403 would be better than exception.

Not really important for me, but I think it would be nice to be consistent with Django. Just an idea, how to improve it :) Thanks anyway for merging this mixin! :+1: