Comment 2 for bug 1796192

Reviewed: https://review.openstack.org/608091
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=3eea37b85b1abc72786a2b24baf01141b4d95f08
Submitter: Zuul
Branch: master

commit 3eea37b85b1abc72786a2b24baf01141b4d95f08
Author: imacdonn <email address hidden>
Date: Thu Oct 4 21:27:18 2018 +0000

    Handle online_data_migrations exceptions

    When online_data_migrations raise exceptions, nova/cinder-manage catches
    the exceptions, prints fairly useless "something didn't work" messages,
    and moves on. Two issues:

    1) The user(/admin) has no way to see what actually failed (exception
       detail is not logged)

    2) The command returns exit status 0, as if all possible migrations have
       been completed successfully - this can cause failures to get missed,
       especially if automated

    This change adds logging of the exceptions, and introduces a new exit
    status of 2, which indicates that no updates took effect in the last
    batch attempt, but some are (still) failing, which requires intervention.

    Change-Id: Ib684091af0b19e62396f6becc78c656c49a60504
    Closes-Bug: #1796192