Replace tearDown with addCleanup in unit tests

[Dave Chen]

tearDown should be replace by addCleanup in the unit tests to avoid stale state if setUp fails or any failure in tearDown method.

There is a bp in cinder project, just copy them here for reference,
"Infra team has indicated that tearDown methods should be replaced with addCleanup in unit tests.
The reason is that all addCleanup methods will be executed even if one of them fails, while a failure in tearDown method can leave the rest of the tearDown un-executed, which can leave stale state laying around.

Moreover, tearDown methods won't run if an exception raises in setUp method, while addCleanup will run in such case.

So, we should replace tearDown with addCleanup methods."

Since the tearDown method is not used widely in keystone sub-project, so just file a bug to track the change."

The link of the reference: https://blueprints.launchpad.net/cinder/+spec/replace-teardown-with-addcleanup

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/207753

[Dave Chen (wei-d-chen)]

Interesting, this poster explained well about the behavior of teardown, http://pythontesting.net/framework/unittest/unittest-wrong-teardown/.

[Dolph Mathews (dolph)]

FWIW, I don't think it's necessary to file a bug for refactors. I also think it's completely ridiculous to file a blueprint, given that a pure refactor has absolutely zero impact on end users.

[Dave Chen (wei-d-chen)]

@Dolph, I agree, this should be just a refactor, it's not worth a BP and not even a bug.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/207753
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=6a8825ebb06dec9d5263667570fb85ba26e10647
Submitter: Jenkins
Branch: master

commit 6a8825ebb06dec9d5263667570fb85ba26e10647
Author: Dave Chen <email address hidden>
Date: Fri Jul 31 14:58:10 2015 +0800

    Cleanup tearDown in unit tests

    Infra team has indicated that tearDown should not be used and should
    be replaced with addCleanup in all places.

    Any failure in tearDown methods can leave the rest of the tearDown
    un-executed, which can leave stale state laying around.

    Cleanup items are called even if setUp fails (unlike tearDown).

    - Remove tearDown in test_ldap_livetest.py since it doesn't add any
      functionality.
    - Replace tearDown with addCleanup in test_sql_upgrade.py, and split
      the original tearDown into three parts, so any failure of them won't
      affect other addCleanup methods's execution.

    Change-Id: I6011d066ef928347772313221277cc641e4dd0a3
    Closes-Bug: #1480119