cinder list-volumes.yaml fails with NoneType is not callable

[Walt Boring]

└─[$] < > python --version
Python 3.8.5

└─[$] < > rally task start list-volumes.yaml
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Preparing input task
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Task is:
---
  CinderVolumes.list_volumes:
    -
      args:
        detailed: True
      runner:
        type: "constant"
        times: 100
        concurrency: 1
      context:
        volumes:
          size: 1
          volumes_per_tenant: 4
      sla:
        failure_rate:
          max: 0

Task syntax is correct :)
Running Rally version 3.2.0
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Task 9504d777-c258-4e17-a9c9-5b6ab7924bed: started
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Running Task... This can take a while...

To track task status use:

 rally task status
 or
 rally task detailed

Using task: 9504d777-c258-4e17-a9c9-5b6ab7924bed
2020-11-05 13:43:50.792 71669 INFO rally.task.engine [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Starting: Task validation.
2020-11-05 13:43:50.796 71669 INFO rally.task.engine [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Starting: Task validation of syntax.
2020-11-05 13:43:50.802 71669 INFO rally.task.engine [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Completed: Task validation of syntax.
2020-11-05 13:43:50.802 71669 INFO rally.task.engine [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Starting: Task validation of required platforms.
2020-11-05 13:43:50.809 71669 INFO rally.task.engine [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Completed: Task validation of required platforms.
2020-11-05 13:43:50.810 71669 INFO rally.task.engine [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Starting: Task validation of semantic.
2020-11-05 13:43:50.810 71669 INFO rally.task.engine [-] Check health of the environment '105ac33b-bc07-46e2-85ec-a3e43d786a8f'.
2020-11-05 13:43:52.772 71669 INFO rally.task.engine [-] Platform existing@openstack (available: True): OK!
2020-11-05 13:43:54.302 71669 INFO rally.task.context [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Context users@openstack setup() finished in 1.52 sec
2020-11-05 13:43:55.836 71669 INFO rally.task.context [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Context users@openstack cleanup() started
2020-11-05 13:43:55.836 71669 INFO rally.task.context [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Context users@openstack cleanup() finished in 0.20 msec
2020-11-05 13:43:55.836 71669 INFO rally.task.engine [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Completed: Task validation of semantic.
2020-11-05 13:43:55.836 71669 INFO rally.task.engine [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Completed: Task validation.
2020-11-05 13:43:55.836 71669 INFO rally.api [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed input file is valid.
2020-11-05 13:43:55.837 71669 INFO rally.api [-] Run Task 9504d777-c258-4e17-a9c9-5b6ab7924bed against Deployment 105ac33b-bc07-46e2-85ec-a3e43d786a8f
2020-11-05 13:43:55.837 71669 INFO rally.task.engine [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Starting: Running task.
2020-11-05 13:43:55.850 71669 INFO rally.task.engine [-] Running workload:
  position = 0
  config = {
   "version": 2,
   "title": "A cropped version of a bigger task.",
   "description": "Auto-generated task from a single workload (uuid=a124531d-ef68-4782-af72-a2151412fab9)",
   "subtasks": [
      {
         "title": "CinderVolumes.list_volumes",
         "description": "List all volumes.",
         "scenario": {
            "CinderVolumes.list_volumes": {
               "detailed": true
            }
         },
         "contexts": {
            "volumes": {
               "size": 1,
               "volumes_per_tenant": 4
            }
         },
         "runner": {
            "constant": {
               "times": 100,
               "concurrency": 1
            }
         },
         "hooks": [],
         "sla": {
            "failure_rate": {
               "max": 0
            }
         }
      }
   ]
}

2020-11-05 13:43:57.467 71669 INFO rally.task.context [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Context users@openstack setup() finished in 1.61 sec
2020-11-05 13:44:23.391 71669 INFO rally.task.context [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Context volumes@openstack setup() finished in 25.92 sec
2020-11-05 13:44:23.397 71669 INFO rally.task.context [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Context volumes@openstack cleanup() started
2020-11-05 13:44:30.617 71669 INFO rally.task.context [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Context volumes@openstack cleanup() finished in 7.22 sec
2020-11-05 13:44:30.617 71669 INFO rally.task.context [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Context users@openstack cleanup() started
2020-11-05 13:44:30.617 71669 INFO rally.task.context [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Context users@openstack cleanup() finished in 0.24 msec
2020-11-05 13:44:31.949 71669 INFO rally.task.engine [-] Load duration is: 0.0
2020-11-05 13:44:31.950 71669 INFO rally.task.engine [-] Full runner duration is: 0.0
2020-11-05 13:44:31.950 71669 INFO rally.task.engine [-] Full duration is: 34.76057
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine [-] Unexpected exception during the workload execution: TypeError: 'NoneType' object is not callable
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine Traceback (most recent call last):
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine File "/Users/i530566/devel/SAP/.rally-venv/lib/python3.8/site-packages/rally/task/engine.py", line 533, in _run_workload
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine runner_obj.run(workload["name"], context_obj,
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine File "/Users/i530566/devel/SAP/.rally-venv/lib/python3.8/site-packages/rally/task/runner.py", line 166, in run
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine self._run_scenario(scenario_plugin, "run", context, args)
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine File "/Users/i530566/devel/SAP/.rally-venv/lib/python3.8/site-packages/rally/plugins/task/runners/constant.py", line 244, in _run_scenario
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine process_pool = self._create_process_pool(
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine File "/Users/i530566/devel/SAP/.rally-venv/lib/python3.8/site-packages/rally/task/runner.py", line 192, in _create_process_pool
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine process.start()
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine File "/Users/i530566/.pyenv/versions/3.8.5/lib/python3.8/multiprocessing/process.py", line 121, in start
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine self._popen = self._Popen(self)
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine File "/Users/i530566/.pyenv/versions/3.8.5/lib/python3.8/multiprocessing/context.py", line 224, in _Popen
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine return _default_context.get_context().Process._Popen(process_obj)
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine File "/Users/i530566/.pyenv/versions/3.8.5/lib/python3.8/multiprocessing/context.py", line 284, in _Popen
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine return Popen(process_obj)
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine File "/Users/i530566/.pyenv/versions/3.8.5/lib/python3.8/multiprocessing/popen_spawn_posix.py", line 32, in __init__
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine super().__init__(process_obj)
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine File "/Users/i530566/.pyenv/versions/3.8.5/lib/python3.8/multiprocessing/popen_fork.py", line 19, in __init__
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine self._launch(process_obj)
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine File "/Users/i530566/.pyenv/versions/3.8.5/lib/python3.8/multiprocessing/popen_spawn_posix.py", line 47, in _launch
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine reduction.dump(process_obj, fp)
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine File "/Users/i530566/.pyenv/versions/3.8.5/lib/python3.8/multiprocessing/reduction.py", line 60, in dump
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine ForkingPickler(file, protocol).dump(obj)
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine TypeError: 'NoneType' object is not callable
2020-11-05 13:44:31.957 71669 ERROR rally.task.engine
2020-11-05 13:44:31.964 71669 INFO rally.task.engine [-] Finished workload 1/1 of subtask 1 (completed 1 of 1 in general).
2020-11-05 13:44:31.974 71669 INFO rally.task.engine [-] Task 9504d777-c258-4e17-a9c9-5b6ab7924bed | Completed: Running task.