The fix for `OSSA-2017-005`_ (CVE-2017-16239) was too far-reaching in that
rebuilds can now fail based on scheduling filters that should not apply
to rebuild. For example, a rebuild of an instance on a disabled compute
host could fail whereas it would not before the fix for CVE-2017-16239.
Similarly, rebuilding an instance on a host that is at capacity for vcpu,
memory or disk could fail since the scheduler filters would treat it as a
new build request even though the rebuild is not claiming *new* resources.
Therefore this release contains a fix for those regressions in scheduling
behavior on rebuild while maintaining the original fix for CVE-2017-16239.
.. note:: The fix relies on a ``RUN_ON_REBUILD`` variable which is checked
for all scheduler filters during a rebuild. The reasoning behind
the value for that variable depends on each filter. If you have
out-of-tree scheduler filters, you will likely need to assess
whether or not they need to override the default value (False)
for the new variable.