Nova error causes StackValidationFailed error

[Steven Hardy]

If nova returns an error looking up images during stack validation, we return a StackValidationFailed, which is a bit misleading since there's actually nothing wrong with the user template. Should probably catch this and return ServerError instead, since this is really an internal error not a validation failure.

engine.log snippet attached, the client output is:

# heat-cfn create wp22 --template-file=/home/shardy/git/heat-templates/cfn/WordPress_Single_Instance.template --parameters="InstanceType=m1.xlarge;DBUsername=${USER};DBPassword=verybadpass;KeyName=${USER}_key;LinuxDistribution=F18"
ERROR:Failed to create. Got error:
ERROR:Data supplied was not valid: <ErrorResponse><Error><Message>A bad or out-of-range value was supplied:The server has either erred or is incapable of performing the requested operation. (HTTP 500) (Request-ID: req-b673fd7d-be5e-40de-afed-5beb4a765fde)</Message><Code>InvalidParameterValue</Code><Type>Sender</Type></Error></ErrorResponse>
[root@t430slt heat]# vim heat/common/exception.py

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/33648

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/33648
Committed: http://github.com/openstack/heat/commit/f1ea0f2d9be21e1a013ed9990f0f86adabb2ecbd
Submitter: Jenkins
Branch: master

commit f1ea0f2d9be21e1a013ed9990f0f86adabb2ecbd
Author: Zhang Lei (Sneeze) <email address hidden>
Date: Wed Jun 26 13:39:42 2013 +0800

    Raise suitable exception when stack validation fails

    fixed Bug#1191009

    If nova returns an error looking up images during stack validation, we
    return a StackValidationFailed, but we should probably catch
    this and return ServerError instead, since this is really an internal
    error not a validation failure.

    Change-Id: Id509b2fa9f78e197cacfe44bae6c3db37cfd6179