Comment 1 for bug 1737500

Reviewed: https://review.openstack.org/559661
Committed: https://git.openstack.org/cgit/openstack/mistral/commit/?id=1ece440ac5f4b613385b44623022421a60256bc7
Submitter: Zuul
Branch: master

commit 1ece440ac5f4b613385b44623022421a60256bc7
Author: Idan Narotzki <email address hidden>
Date: Mon Apr 9 08:37:55 2018 +0000

    Adding WWW-Authenticate info.

    Sometimes when mistral requests are failing with "401 Unauthorized"
    against keycloak, the reason are not mentioned in the logs.

    In case keycloack return 401 it must provide the www-Authenticate
    response header with the reason:
    https://www.w3.org/Protocols/HTTP/1.0/spec.html#WWW-Authenticate

    This code take care of it by adding the WWW-Authenticate value to
    mistral api-log.

    Change-Id: I7ae221aaeb2233184bd4818490e72ff662dca5cb
    Closes-Bug: #1737500