[Fixed]-How to catch a PermissionDenied(403) from Django with Ajax?

You should be able to see HTTP errors in the error handler:

$.ajax({
    ...
    error: function (xhr, ajaxOptions, thrownError) {
        if(xhr.status==403) {
            alert(...);
        }
    }
}

You will always see the 403 in the console as that’s the HTTP response you are getting from the server.

You can simplify the test_func to just:

class AllUsersViews(UserPassesTestMixin, View):
    ...

    def test_func(self):
        return self.request.user.is_superuser

    ...