Comment 4 for bug 1794996

Reviewed: https://review.openstack.org/606106
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=d252f81573cdfe7a0966f134608bb85d17311e33
Submitter: Zuul
Branch: master

commit d252f81573cdfe7a0966f134608bb85d17311e33
Author: Matt Riedemann <email address hidden>
Date: Fri Sep 28 10:58:48 2018 -0400

    Add functional regression test for bug 1794996

    The _destroy_evacuated_instances method on compute
    startup tries to cleanup guests from the hypervisor
    and allocations held against that compute node resource
    provider by evacuated instances, but doesn't take into
    account that those evacuated instances could have been
    deleted in the meantime which leads to a lazy-load
    InstanceNotFound error that kills the startup of the
    compute service.

    This change adds a functional regression test to recreate
    the bug. A subsequent change with the fix will update
    the test to show the bug is fixed.

    Note that assertFlavorMatchesAllocation and
    _boot_and_check_allocations are redefined in the test
    class because If6aa37d9b6b48791e070799ab026c816fda4441c
    refactored those methods which will cause problems with
    backports of this test. The redefined methods will be
    removed in a follow up cleanup patch.

    Change-Id: I19b0d8baea5440f5d5bc49a6956d9a97bf031a05
    Related-Bug: #1794996