openstack overcloud delete command fails

Issue

• openstack overcloud delete command fails with the following error messages.

  (undercloud) [stack@id1-osp16-undercloud ~]$ openstack overcloud delete overcloud
  Are you sure you want to delete this overcloud [y/N]? y
  Undeploying stack overcloud...
  Waiting for messages on queue 'tripleo' with no timeout.
  Deleting plan overcloud...
  The action raised an exception [action_ex_id=aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa, msg='Cannot delete a plan that has an associated stack.', action_cls='<class 'mistral.actions.action_factory.DeletePlanAction'>', attributes='{}', params='{'container': 'overcloud'}']
  Error occurred while deleting plan Exception deleting plan: The action raised an exception [action_ex_id=bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb, msg='Cannot delete a plan that has an associated stack.', action_cls='<class 'mistral.actions.action_factory.DeletePlanAction'>', attributes='{}', params='{'container': 'overcloud'}']
  sys:1: ResourceWarning: unclosed <socket.socket fd=4, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('10.0.0.1', XXXX), raddr=('10.0.0.1', 5000)>
  sys:1: ResourceWarning: unclosed <socket.socket fd=5, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('10.0.0.1', XXXX), raddr=('10.0.0.1', 8004)>
  sys:1: ResourceWarning: unclosed <socket.socket fd=7, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('10.0.0.1', XXXX), raddr=('10.0.0.1', 8989)>