Cannot create an ad-hoc action from another ad-hoc action

[Xavier Hardy]

As an action creator, I must be able to create ad-hoc actions from other ad-hoc actions. Doing so result in a 500 Internal Server error message:

```
AttributeError: 'NoneType' object has no attribute 'rpartition'
Traceback (most recent call last):

  File "/home/user/env/local/lib/python2.7/site-packages/oslo_messaging/rpc/server.py", line 133, in _process_incoming
    res = self.dispatcher.dispatch(message)

  File "/home/user/env/local/lib/python2.7/site-packages/oslo_messaging/rpc/dispatcher.py", line 150, in dispatch
    return self._do_dispatch(endpoint, method, ctxt, args)

  File "/home/user/env/local/lib/python2.7/site-packages/oslo_messaging/rpc/dispatcher.py", line 121, in _do_dispatch
    result = func(ctxt, **new_args)

  File "/home/user/env/local/lib/python2.7/site-packages/mistral/engine/rpc.py", line 141, in start_action
    **params

  File "/home/user/env/local/lib/python2.7/site-packages/mistral/utils/__init__.py", line 113, in _logged
    return func(*args, **kw)

  File "/home/user/env/local/lib/python2.7/site-packages/mistral/engine/default_engine.py", line 82, in start_action
    action.schedule(action_input, target)

  File "/home/user/env/local/lib/python2.7/site-packages/mistral/engine/actions.py", line 209, in schedule
    desc=desc

  File "/home/user/env/local/lib/python2.7/site-packages/mistral/engine/actions.py", line 134, in _create_action_execution
    self.action_def.attributes or {}) and self.task_ex:

  File "/home/user/env/local/lib/python2.7/site-packages/mistral/services/action_manager.py", line 179, in has_action_context
    return _has_argument(action, attributes, _ACTION_CTX_PARAM)

  File "/home/user/env/local/lib/python2.7/site-packages/mistral/services/action_manager.py", line 172, in _has_argument
    action_cls = action_factory.construct_action_class(action, attributes)

  File "/home/user/env/local/lib/python2.7/site-packages/mistral/actions/action_factory.py", line 20, in construct_action_class
    action_class = importutils.import_class(action_class_str)

  File "/home/user/env/local/lib/python2.7/site-packages/oslo_utils/importutils.py", line 29, in import_class
    mod_str, _sep, class_str = import_str.rpartition('.')

AttributeError: 'NoneType' object has no attribute 'rpartition'
```

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/334312
Committed: https://git.openstack.org/cgit/openstack/mistral/commit/?id=024d93801d7c26651a9c021323611be7a8dc6fa4
Submitter: Jenkins
Branch: master

commit 024d93801d7c26651a9c021323611be7a8dc6fa4
Author: Xavier Hardy <email address hidden>
Date: Mon Jun 27 10:25:41 2016 +0200

    Support recursive ad-hoc action definitions

    A ad-hoc action can be based on another ad-hoc actions,
    allowing several level of abstractions in actions.

    Change-Id: I321bbf798b2801041a83530152d0cd73d8bc7c01
    Closes-Bug: #1591217

[Doug Hellmann (doug-hellmann)]

This issue was fixed in the openstack/mistral 3.0.0.0b2 development milestone.