Refactor use of oslo.db.sqlalchemy.session.EngineFacade because it's deprecated

[Vivek Dhayaal]

OsloDBDeprecationWarning shows up in many gerrit patches' gate-keystone-python27 console logs.
<snip>
...
2015-08-31 11:12:43.194 | {2} keystone.tests.unit.backend.domain_config.test_sql.SqlDomainConfigModels.test_whitelisted_model [0.467583s] ... ok
2015-08-31 11:12:43.194 |
2015-08-31 11:12:43.194 | Captured stderr:
2015-08-31 11:12:43.194 | ~~~~~~~~~~~~~~~~
2015-08-31 11:12:43.194 | /home/jenkins/workspace/gate-keystone-python27/.tox/py27/local/lib/python2.7/site-packages/oslo_db/sqlalchemy/enginefacade.py:1015: OsloDBDeprecationWarning: EngineFacade is deprecated; please use oslo.db.sqlalchemy.enginefacade
2015-08-31 11:12:43.195 | expire_on_commit=expire_on_commit, _conf=conf)
2015-08-31 11:12:43.195 |
2015-08-31 11:12:43.195 | {2} keystone.tests.unit.backend.role.test_ldap.LdapIdentitySqlEverythingElseRole.test_list_roles [0.319631s] ... ok
...
</snip>

Few instances:
https://review.openstack.org/#/c/217340/
http://logs.openstack.org/40/217340/2/check/gate-keystone-python27/4cfcaaf/console.html

https://review.openstack.org/#/c/210456/
http://logs.openstack.org/56/210456/6/check/gate-keystone-python27/da1ad9f/console.html

https://review.openstack.org/#/c/209524/
http://logs.openstack.org/24/209524/13/check/gate-keystone-python27/8a97dbd/console.html

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/218983

[OpenStack Infra (hudson-openstack)]

Change abandoned by Tom Cocozzello (<email address hidden>) on branch: master
Review: https://review.openstack.org/218983

[Tom Cocozzello (tjcocozz-deactivatedaccount)]

It looks like I bit off more than I could chew with this bug. What is happening is that oslo is making the use of the SQLAlchemy Engine more standardized.

Here is a link that goes more in depth about the change:
http://specs.openstack.org/openstack/oslo-specs/specs/kilo/make-enginefacade-a-facade.html

Here is a review from Ironic that is similar to what I think we need to do to make this change:
https://review.openstack.org/#/c/191801/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/257458

[Steve Martinelli (stevemar)]

confirmed with dims that this will not be removed in the M release, but we should prioritize this for N, setting priority to High.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/257458
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=0e156737d0e5aabb86c0fdb326dc9c95d52b3e32
Submitter: Jenkins
Branch: master

commit 0e156737d0e5aabb86c0fdb326dc9c95d52b3e32
Author: Grzegorz Grasza <email address hidden>
Date: Mon Dec 14 17:07:46 2015 +0100

    Use the new enginefacade from oslo.db

    EngineFacade is deprecated. This partially switches keystone to
    use oslo.db.sqlalchemy.enginefacade. 'get_session' and 'get_engine'
    methods are still used in sql migrations and related tests.

    Change-Id: I221232d50821fe2adb9881f237f06714003ce79d
    Partial-Bug: #1490571

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/284516

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/284516
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=8f432e9b4492ff474c16fbcd48b33e8f5aa0e661
Submitter: Jenkins
Branch: master

commit 8f432e9b4492ff474c16fbcd48b33e8f5aa0e661
Author: Morgan Fainberg <email address hidden>
Date: Wed Feb 24 19:29:20 2016 -0800

    No more legacy engine facade in tests

    Do not use the legacy engine facade from oslo_db even in testing.

    Change-Id: I70d0724679a5fd5cd3ace54e4ae44957c2277daf
    Closes-Bug: #1490571

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/284521
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=e959badd7157fcc94abfa757e636b5f97ffaad09
Submitter: Jenkins
Branch: master

commit e959badd7157fcc94abfa757e636b5f97ffaad09
Author: Morgan Fainberg <email address hidden>
Date: Wed Feb 24 19:48:25 2016 -0800

    Remove get_session and get_engine

    Remove the get_session and get_engine methods. These are not
    supported anymore as the get_session_for_read() and
    get_session_for_write() are now in place. This also prevents the use
    of the LegacyEngineFacade.

    Change-Id: Ie9eb824d07e641b713346a03a0aa15d8ab16c338
    Related-Bug: #1490571

[Thierry Carrez (ttx)]

This issue was fixed in the openstack/keystone 9.0.0.0b3 development milestone.