Function launch 

pub fn launch(
    env: &Env,
    name: &str,
    exe: &str,
    args: &[String],
    wait: Duration,
) -> Result<(Session, Client), String>

Start exe args… --control <port> with its key folder in the session folder and its output in the session log, and wait until it answers app.ping (or exits, or wait passes). An app that ignores ASHLAR_CONTROL_KEY_DIR is still found: its key is looked for in the settings folders.