NoSuchOptError thrown for bad choice value in StrOpt

[Davanum Srinivas (DIMS)]

Reported by Anton Arefiev. If we have a StrOpt with a choices parameter and a config file with a wrong value, we end up throwing a NoSuchOptError.

2015-09-23 17:31:41.832 TRACE ironic Traceback (most recent call last):
2015-09-23 17:31:41.832 TRACE ironic File "/usr/local/bin/ironic-api", line 10, in <module>
2015-09-23 17:31:41.832 TRACE ironic sys.exit(main())
2015-09-23 17:31:41.832 TRACE ironic File "/opt/stack/ironic/ironic/cmd/api.py", line 50, in main
2015-09-23 17:31:41.832 TRACE ironic app.VersionSelectorApplication(),
2015-09-23 17:31:41.832 TRACE ironic File "/opt/stack/ironic/ironic/api/app.py", line 98, in __init__
2015-09-23 17:31:41.832 TRACE ironic pc.app.enable_acl = (CONF.auth_strategy == 'keystone')
2015-09-23 17:31:41.832 TRACE ironic File "/usr/local/lib/python2.7/dist-packages/oslo_config/cfg.py", line 1902, in __getattr__
2015-09-23 17:31:41.832 TRACE ironic raise NoSuchOptError(name)
2015-09-23 17:31:41.832 TRACE ironic NoSuchOptError: no such option: auth_strategy

We should expose the original message which is thrown here, as it shows correctly that the option is defined correctly and it's just the value is wrong.
https://github.com/openstack/oslo.config/blob/master/oslo_config/types.py#L79

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/226993

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/226993
Committed: https://git.openstack.org/cgit/openstack/oslo.config/commit/?id=934ae9b34f7ab4bba5b1a4573a714d803a4c1707
Submitter: Jenkins
Branch: master

commit 934ae9b34f7ab4bba5b1a4573a714d803a4c1707
Author: Davanum Srinivas <email address hidden>
Date: Wed Sep 23 16:55:10 2015 -0400

    Fix bad exception for StrOpt with invalid choice value

    If there's a StrOpt with name foo and say choices ['bar', 'baz'] and the
    config file has a bad value for foo (say 'boo'), then the end user
    will see:
    NoSuchOptError: no such option: foo

    Which gives the wrong impression that somehow the foo was never registered
    which is wrong!

    They should see this instead:
    oslo_config.cfg.ConfigFileValueError: Value for option foo is not
    valid: Valid values are [bar, baz], but found 'boo'

    Closes-Bug: #1499074
    Change-Id: I694d8aa99c861c7b47bae77ef12f435b7c3712ab