validation exceptions are not handled correctly

[Nikita Konovalov]

Error message is lost for all validation exceptions.

2013-09-03 17:04:27.079 38438 DEBUG savanna.utils.api [-] Validation Error occurred: error_code=400, error_message=An unknown exception occurred, error_name=NOT_SINGLE_NAME_NODE bad_request /Users/nikitakonovalov/work/savanna/.tox/venv/lib/python2.7/site-packages/savanna/utils/api.py:236
127.0.0.1 - - [03/Sep/2013 17:04:27] "POST /v1.1/73ac77203fa744eaa31b853593a87c10/clusters HTTP/1.1" 400 225 0.712008

Horizon displays wrong message:
 'An unknown exception occurred'
while expected is:
'Hadoop cluster should contain only 1 NameNode instance. Actual NN count is 0'

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/47132

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/47132
Committed: http://github.com/stackforge/savanna/commit/f2a4b321731571013ceb4e89b3402322e6998f71
Submitter: Jenkins
Branch: master

commit f2a4b321731571013ceb4e89b3402322e6998f71
Author: Andrew Lazarev <email address hidden>
Date: Wed Sep 18 15:38:34 2013 +0400

    Fixed wrong usage of SavannaException

    Added defence against such wrong usage

    Fixes bug #1220239

    Change-Id: I391fe61a14987cac9c2a565b5049de22e1bbc9ae