Expose action server result when handling failures

[fifi-reframe]

I'm using the bt_action_node to call a server that implements a FollowJointTrajectory action. I'd like to be able to handle different error codes that are set by the server when the trajectory is aborted or canceled. In the current implementation, the WrappedResult is not exposed to the onFailure handler. Is there a recommended way to be able to handle error codes, or more generally consume the action result on a failure?