---
upgrade:
  - |
    The libvirt driver's RBD imagebackend no longer supports setting
    force_raw_images to False. Setting force_raw_images = False and
    images_type = rbd in nova.conf will cause the nova compute service
    to refuse to start. To fix this, set force_raw_images = True. This
    change was required to fix the `bug 1816686`_.

    Note that non-raw cache image files will be removed if you set
    force_raw_images = True and images_type = rbd now.

    .. _bug 1816686: https://bugs.launchpad.net/nova/+bug/1816686
