Function event_to_task 

pub(crate) fn event_to_task(
    qt: &CxxQtThread<Sioul>,
    shared: &Arc<Shared>,
    key: &str,
) -> String

An event made a task (key, its file): in the usual list, its time its block’s when still to come and not repeating, then the event taken out. Returns what went wrong, else “”.