Comment 3 for bug 1238453

Reviewed: https://review.openstack.org/66757
Committed: https://git.openstack.org/cgit/openstack/ceilometer/commit/?id=a1b1fdac6a432ddeb4d265a19e7b945a16a19bba
Submitter: Jenkins
Branch: master

commit a1b1fdac6a432ddeb4d265a19e7b945a16a19bba
Author: Pradeep Kilambi <email address hidden>
Date: Tue Jan 14 19:46:27 2014 -0800

    Fix to handle null threshold_rule values

    check if threshold_rule and combination_rule values
    are None and raise the right error in the validation
    method instead of propagating it further causing
    unhandled exceptions.

    fixes bug #1238453

    Change-Id: I70a397c89d974e489fd0ccc4ab28d73aed51443f