Task config is valid :)
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Task  0eb388b9-b621-490c-9e66-b7fe8f244738: started
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Benchmarking... This can take a while...

To track task status use:

        rally task status
        or
        rally task detailed

Using task: 0eb388b9-b621-490c-9e66-b7fe8f244738
2017-03-06 13:18:11.042 21236 INFO rally.api [-] Benchmark Task 0eb388b9-b621-490c-9e66-b7fe8f244738 on Deployment fec04a79-d55f-4d78-8122-d109aa97b73f
2017-03-06 13:18:11.046 21236 INFO rally.task.engine [-] Task 0eb388b9-b621-490c-9e66-b7fe8f244738 | Starting:  Benchmarking.
2017-03-06 13:18:11.134 21236 INFO rally.task.engine [-] Running benchmark with key: 
{
  "kw": {
    "runner": {
      "type": "constant", 
      "times": 1000, 
      "concurrency": 10
    }, 
    "args": {
      "number_of_names": 100
    }, 
    "sla": {
      "max_avg_duration_per_atomic": {
        "generate_100_names": 0.015
      }, 
      "failure_rate": {
        "max": 0
      }
    }
  }, 
  "name": "RallyProfile.generate_names_in_atomic", 
  "pos": 0
}
2017-03-06 13:18:13.149 21236 INFO rally.task.engine [-] Load duration is: 0.0
2017-03-06 13:18:13.149 21236 INFO rally.task.engine [-] Full runner duration is: 0.0
2017-03-06 13:18:13.150 21236 INFO rally.task.engine [-] Full duration is: 0.00157
2017-03-06 13:18:13.180 21236 RALLYDEBUG rally.task.engine [-] Traceback (most recent call last):
  File "/home/akurilin/projects/openstack/rally/rally/task/engine.py", line 454, in run
    with context.ContextManager(context_obj):
  File "/home/akurilin/projects/openstack/rally/rally/task/context.py", line 192, in __enter__
    self.cleanup()
  File "/home/akurilin/projects/openstack/rally/rally/task/context.py", line 180, in cleanup
    ctxlst = self._visited or self._get_sorted_context_lst()
  File "/home/akurilin/projects/openstack/rally/rally/task/context.py", line 165, in _get_sorted_context_lst
    for ctx_name in self.context_obj["config"].keys()])
  File "/home/akurilin/projects/openstack/rally/rally/common/plugin/plugin.py", line 245, in get
    hint=hint)
MultipleMatchesFound: Found multiple users at any of namespaces: users, users. Hint: Try to choose the correct Plugin base or namespace to search in.