destroy-controller reports warning endlessly

[Brad Crittenden]

Trying to destroy a controller and all models results in a scrolling error message that does not stop until the command is killed.

$ juju destroy-controller ec2-trusty --destroy-all-models
WARNING! This command will destroy the "ec2-trusty" controller.
This includes all machines, services, data and other resources.

Continue [y/N]? y
Destroying controller "ec2-trusty"
Waiting for hosted model resources to be reclaimed.
All hosted models reclaimed, cleaning up controller machines
WARNING could not delete security group "juju-640fe9e1-6a8d-40fc-8046-5f7865cb8e42-0": There are active instances using security group 'juju-640fe9e1-6a8d-40fc-8046-5f7865cb8e42-0' (InvalidGroup.InUse)
WARNING could not delete security group "juju-640fe9e1-6a8d-40fc-8046-5f7865cb8e42-0": There are active instances using security group 'juju-640fe9e1-6a8d-40fc-8046-5f7865cb8e42-0' (InvalidGroup.InUse)
WARNING could not delete security group "juju-640fe9e1-6a8d-40fc-8046-5f7865cb8e42-0": There are active instances using security group 'juju-640fe9e1-6a8d-40fc-8046-5f7865cb8e42-0' (InvalidGroup.InUse)
WARNING could not delete security group "juju-640fe9e1-6a8d-40fc-8046-5f7865cb8e42-0": There are active instances using security group 'juju-640fe9e1-6a8d-40fc-8046-5f7865cb8e42-0' (InvalidGroup.InUse)
WARNING could not delete security group "juju-640fe9e1-6a8d-40fc-8046-5f7865cb8e42-0": There are active instances using security group 'juju-640fe9e1-6a8d-40fc-8046-5f7865cb8e42-0' (InvalidGroup.InUse)
[repeat]
^C