Comment 8 for bug 1978729

Reviewed: https://review.opendev.org/c/openstack/cinder/+/867023
Committed: https://opendev.org/openstack/cinder/commit/1bc0b9caba955d73389e6b88bfd9fa40b942f3aa
Submitter: "Zuul (22348)"
Branch: stable/yoga

commit 1bc0b9caba955d73389e6b88bfd9fa40b942f3aa
Author: Jesper Schmitz Mouridsen <email address hidden>
Date: Fri Jun 17 10:29:00 2022 +0000

    Serialize message_* properties of RequestContext

    Change Idc00b125b33b added the ability to store and retrieve user
    message data in the request context, but it neglected to add code to
    make sure they would persist across serialization and deserialization
    of the request context object, as happens in the create-backup
    workflow. As a result, when a user message needed to be created to
    describe an error condition in the backup driver, instead we'd get an
    exception raised: "TypeError: 'NoneType' object is not subscriptable".

    This patch fixes the issue by making sure the message_* properties
    persist across serialization/deserialization of RequestContext objects.

    Closes-Bug: 1978729
    Change-Id: Ibdaaf39abafbae6bfcb9fdf9fb7a55d968ad9f11
    Signed-off-by: Jesper Schmitz Mouridsen <email address hidden>
    (cherry picked from commit c46d41719e0c8199dc17ef566413889692644ef5)