Comment 16 for bug 1824315

Reviewed: https://review.opendev.org/660325
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=2f7b1031a9b80d15052fcd9b22831f1db0486a4a
Submitter: Zuul
Branch: stable/stein

commit 2f7b1031a9b80d15052fcd9b22831f1db0486a4a
Author: melanie witt <email address hidden>
Date: Wed May 15 20:51:41 2019 +0000

    Stop logging traceback when skipping quiesce

    During snapshot of a volume-backed instance, we attempt to quiesce the
    instance before doing the snapshot. If quiesce is not supported or the
    qemu guest agent is not enabled, we will skip the quiesce and move on
    to the snapshot.

    Because quiesce is a call to nova-compute over RPC, when the libvirt
    driver raises QemuGuestAgentNotEnabled, oslo.messaging will append the
    full traceback to the exception message [1] for the remote caller. So,
    a LOG.info(..., exp) log of the exception object will result in a log
    of the full traceback. Logging of the full traceback causes confusion
    for those debugging CI failures.

    We would rather not log the full traceback in this case where we are
    catching the exception and emitting an INFO message, so we should use
    exp.format_message() instead of oslo.messaging's __str__ override.

    [1] https://github.com/openstack/oslo.messaging/blob/40c25c2/oslo_messaging/_drivers/common.py#L212

    Related-Bug: #1824315

    Change-Id: Ibfedcb8814437c53081f5a2993ab84b25d73e557
    (cherry picked from commit 66070416ab670daf4734f2c30ad2df5d96e615e6)