InternalServerError: Request Failed: internal server error while processing your request.

Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/rally/task/runner.py", line 71, in _run_scenario_once
    getattr(scenario_inst, method_name)(**scenario_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/rally/plugins/openstack/scenarios/neutron/network.py", line 230, in run
    self._delete_subnet(subnet)
  File "/usr/local/lib/python2.7/dist-packages/rally/task/atomic.py", line 91, in func_atomic_actions
    f = func(self, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/rally/plugins/openstack/scenarios/neutron/utils.py", line 191, in _delete_subnet
    self.clients("neutron").delete_subnet(subnet["subnet"]["id"])
  File "/usr/local/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 848, in delete_subnet
    return self.delete(self.subnet_path % (subnet))
  File "/usr/local/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 350, in delete
    headers=headers, params=params)
  File "/usr/local/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 331, in retry_request
    headers=headers, params=params)
  File "/usr/local/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 294, in do_request
    self._handle_fault_response(status_code, replybody, resp)
  File "/usr/local/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 269, in _handle_fault_response
    exception_handler_v20(status_code, error_body)
  File "/usr/local/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 93, in exception_handler_v20
    request_ids=request_ids)
InternalServerError: Request Failed: internal server error while processing your request.
Neutron server returns request_ids: ['req-0cffe429-d777-4517-8d1f-c89c8549486a']