Function mg::blocking_yes_no_question

pub fn blocking_yes_no_question<COMM, SETT>(
    mg: &EventStream<<Mg<COMM, SETT> as Update>::Msg>, 
    msg: String
) -> bool where
    COMM: Clone + EnumFromStr + EnumMetaData + SpecialCommand + 'static,
    SETT: Default + EnumMetaData + Settings + SettingCompletion + 'static, 

Show a blocking yes/no question.