Comment 7 for bug 1554625

Reviewed: https://review.openstack.org/333309
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=3cb015e41015679af71c788b516c7de8280f3a30
Submitter: Jenkins
Branch: stable/liberty

commit 3cb015e41015679af71c788b516c7de8280f3a30
Author: Zane Bitter <email address hidden>
Date: Tue Mar 8 11:35:12 2016 -0500

    Catch exceptions calculating implicit dependencies

    Uncaught exceptions in an overridden add_dependencies() method of a plugin
    can prevent a stack being loaded from the database. To protect against
    programming errors that can result in uncaught exceptions, separate the
    calculation of implicit dependencies out from the calculation of explicit
    dependencies, and ignore exceptions in the latter when dealing with an
    existing stack.

    Change-Id: I939dba57eeba5710bb77a1b30a872fca5d38ad71
    Closes-Bug: #1554625
    (cherry picked from commit 38a46e8d21602e1ebed22c38ba53c0095c6be609)