Driver required libraries are not included in requirements.txt

[Clint Byrum]

Which driver is used is a deployer decision, but the library cannot function without them. So requirements.txt should list all necessary external requirements needed to use the library.

This manifests in TripleO currently by deploying a non-functioning keystone which now depends on oslo.messaging and thus has no MQ driver available for notifications:

2014-03-05 19:36:08.313 2775 ERROR keystone.notifications [-] Failed to construct notifier
2014-03-05 19:36:08.313 2775 TRACE keystone.notifications Traceback (most recent call last):
2014-03-05 19:36:08.313 2775 TRACE keystone.notifications File "/opt/stack/venvs/keystone/local/lib/python2.7/site-packages/keystone/notifications.py", line 175, in _get_notifier
2014-03-05 19:36:08.313 2775 TRACE keystone.notifications transport = messaging.get_transport(CONF)
2014-03-05 19:36:08.313 2775 TRACE keystone.notifications File "/opt/stack/venvs/keystone/local/lib/python2.7/site-packages/oslo/messaging/transport.py", line 185, in get_transport
2014-03-05 19:36:08.313 2775 TRACE keystone.notifications raise DriverLoadFailure(url.transport, ex)
2014-03-05 19:36:08.313 2775 TRACE keystone.notifications DriverLoadFailure: Failed to load transport driver "rabbit": No 'oslo.messaging.drivers' driver found, looking for 'rabbit'

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/78424

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/78426

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/78426
Committed: https://git.openstack.org/cgit/openstack/tripleo-image-elements/commit/?id=1105e565a0917feada1a7e74bf5fe49d8fb3a161
Submitter: Jenkins
Branch: master

commit 1105e565a0917feada1a7e74bf5fe49d8fb3a161
Author: Clint Byrum <email address hidden>
Date: Wed Mar 5 13:42:55 2014 -0800

    Work around missing kombu requirement for keystone

    Keystone has switched to oslo.messaging and thus is missing a
    requirement for the backend drivers.

    We only use kombu, so we can force it in until oslo.messaging is fixed.

    Change-Id: I2ffb6683f51c70d67da043a4907ba84330e75b9f
    Closes-Bug: #1288425

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/78424
Committed: https://git.openstack.org/cgit/openstack/oslo.messaging/commit/?id=52bc704b6e5412ed2bc2ea41e4b6398873f0ac3d
Submitter: Jenkins
Branch: master

commit 52bc704b6e5412ed2bc2ea41e4b6398873f0ac3d
Author: Clint Byrum <email address hidden>
Date: Wed Mar 5 13:38:51 2014 -0800

    Add kombu driver library to requirements.txt

    The RabbitMQ driver is the default driver for oslo.messaging, so it
    makes some sense to require this by default. This is consistent with
    the way e.g. Nova has always required kombu.

    Change-Id: Ibcab58e3f3edce794b571cfabc0a5bcf96c9b47e
    Closes-Bug: #1288425