Looks like this defaulted to false before. Given that the default onFailure will wrap it in an exception (I think?), the default_success changes the behaviour of things using the SshFeed. The problem is that the user's onSuccess is taking SshPollValue so will presumably be using stdout/stderr/errcode already. With this change, existing code will not be called I believe. Need to search our code for everywhere one is supplying onSuccess to decide if we need to also do that onFailure.