Тройное отрицание

gistfile1.py

    if not article.is_visible or not article.is_moderate:

        is_author = article.author == request.user
        if request.user.is_admin or request.user.is_staff or is_author:
            pass
        else:
            raise PermissionDenied


#EDITED

    if not article.is_visible or not article.is_moderate:
 
        is_author = article.author == request.user
        if not (request.user.is_admin or request.user.is_staff or is_author):
           raise PermissionDenied