Fixed #23847 -- Improved the email_check example in the auth documentation.

checks to make sure the user has an email in the desired domain::

    def my_view(request):

        if not '@example.com' in request.user.email:

        if not request.user.email.endswith('@example.com'):

            return HttpResponse("You can't vote in this poll.")

        # ...

        from django.contrib.auth.decorators import user_passes_test

        def email_check(user):

            return '@example.com' in user.email

            return user.email.endswith('@example.com')

        @user_passes_test(email_check)

        def my_view(request):