---
fixes:
  - |
    Nova now ensures that an instance cannot move between availability zones
    when the host of the instance is added or removed to an aggregate that is
    part of another availability zone. Moving from or to the default
    availability zone is also rejected.

    This resolves `bug 1907775`_ where after such move the instance become
    stuck in between availability zones.

    .. _bug 1907775: https://bugs.launchpad.net/nova/+bug/1907775