Unexpected exception message when use %(message)s

[Kiyohiro Adachi]

Bad example:
  raise exception.VolumeDriverException(message="Oorah")
  ==> cinder.exception.VolumeDriverException: Oorah

Good example:
  raise exception.VolumeDriverException(message="Oorah")
  ==> cinder.exception.VolumeDriverException: Volume driver reported an error: Oorah

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/78115

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/132465

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/132465
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=9cd907a8377a4c112ce46755ab68b384ceac75c7
Submitter: Jenkins
Branch: master

commit 9cd907a8377a4c112ce46755ab68b384ceac75c7
Author: Eduardo Costa <email address hidden>
Date: Sun Nov 2 16:06:12 2014 +0100

    Fix exception message formatting

    If the exception class made a reference to the "message" field in
    its format string, it would be overriden with the value of the
    "message" argument itself. It is now possible to use the "message"
    field and preserve the desired message formatting. Test cases
    provided.

    Change-Id: I5705203466535fa242d13e43571012e5bf72712a
    Closes-Bug: #1288066