In Pike, Heat loads any attribute values required to serve an API call at the beginning of the call. If an exception occurs loading any of these values, then the API call will fail. An error in an output of a nested stack causes an exception to be raised in the parent stack if that output is referenced as an attribute of the parent resource. Thus, once this occurs showing the root stack with output resolution will fail, as will operations like stack updates.
Backport is merged to stable/pike upstream.
verified by heat_integrationtests.functional.test_stack_outputs, tested passed
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHEA-2017:3462