We need to add a flag to `emit.open_stream`, something like `sub_with_timestamps` (defaults to `False`), which would mean that the executed stuff will add its own timestamp, so in that case Craft CLI won't add the timestamp to the message This way, if we use emit.open_stream on something that has it's own Craft CLI stuff (or adds timestamps in some way), the outer timestamp will not be present; but if we run whatever (e.g. pip) it will add the timestamps as currently does.