Exception with log message overidden after being set in exception.handle

[Sam Betts]

If a message is passed into exception.handle user_message is set then immediately replaced so the exception never makes it into the log message.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/221000

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/221000
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=5ca1a5230025a6b66bd90467692e9541c9fff52d
Submitter: Jenkins
Branch: master

commit 5ca1a5230025a6b66bd90467692e9541c9fff52d
Author: Sam Betts <email address hidden>
Date: Mon Sep 7 14:32:02 2015 +0100

    Ensure exc message is included in user_message

    In exception.handle the user_message was being overridden so
    failed to include the exception message even if %(exc)s was in
    the message. This patch ensures the correct user_message is
    produced by exception.handle()

    Change-Id: I2bcc041a2f8a3b929c1acbbf3d3ff1e76b5646e9
    Closes-Bug: #1493025