Test suite requires kombu and carrot to be installed

[Dave Walker]

Resolving Bug 798876, switch from Carrot to Kombu allowed backwards support for both modules.

Currently, if only one is available the test suite fails. If importing carrot fails the test suite should SKIP the test, rather than FAIL.

Thanks.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/7029

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/7029
Committed: http://github.com/openstack/nova/commit/a7e4fd35862e6f515c4384a37afdad5dd730c51a
Submitter: Jenkins
Branch: master

commit a7e4fd35862e6f515c4384a37afdad5dd730c51a
Author: Russell Bryant <email address hidden>
Date: Wed May 2 12:14:56 2012 -0400

    Make kombu support optional for running unit tests.

    Fix bug 838386.

    Previously, the unit tests required kombu to be installed to run. This
    patch makes it so the unit tests will still complete successfully, even
    if kombu is not installed.

    Change-Id: I06831a37f8c857bbfd0bce1b1c3aeda7d341a589