auth_required fails with werkzeug >= 0.15
We use the argument response to set the proper headers on the exception.
But werkzeug >= 0.15 remove the response argument but provide www_authenticate argument. This is a non backward compatible change.
I made a PR to restore the argument [1] if they do not accept it, we will need to test the version of werkzeug and call abort differently for each version.
[1] https://github.com/pallets/werkzeug/pull/1527