Comment 8 for bug 1518458

Reviewed: https://review.openstack.org/249324
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=775b862cf04d1a55069bd07b82f2bbcd2361c140
Submitter: Jenkins
Branch: stable/liberty

commit 775b862cf04d1a55069bd07b82f2bbcd2361c140
Author: Zane Bitter <email address hidden>
Date: Fri Nov 20 21:27:13 2015 -0500

    Fix HTTP error codes due to invalid templates

    This reverts commit 9a4d719ea1a6ca63f527b5c78308fd288058d42b and creates a
    new exception type, InvalidGlobalResource, that is raised when a
    non-existent template is referenced in the global environment and which
    results in an HTTP 500 error.

    This fixes the cases where we could return 404 or 500 errors as a result of
    template validation failures, when we should return a 400 error.

    Change-Id: I3c7b3182957448bb13514696cc2e12f5aaddd253
    Closes-Bug: #1518458
    Related-Bug: #1447194
    (cherry picked from commit 517f91ce27299a2a1e4551a8310e3a1ce1151b09)