use bridgeTalk with onError event, exception handling

Hi all,

I'm writting a function who use bridgeTalk to execute a photoshop script. This function works but I would like to throw an exception if the script has a problem. I commented a line in my script to have an exception but the onError event doesn't throw my Error.

Have someone an idea?

Thanks!

function save_to_PSD(obj){
    var bt = new BridgeTalk();
     bt.target = "photoshop";
     bt.body = save_to_psd_function.toSource()+"("+obj.toSource()+");";
     bt.onError = function(errObj) {
        // the next line display the error in the console
        $.writeln(errObj.body);
        // PROBLEM this error is never throw 
        throw new Error (errObj.body);
     };
     bt.send(100);
}
function save_to_psd_function(serializedObject){
    app.displayDialogs = DialogModes.NO;
    var obj = eval(serializedObject);
    var file_path = decodeURI(obj.file_path);
    // this will generate an exception
    //var img_file = new File(file_path);
    var ps_doc = app.open(img_file);
    psdSaveOption = new PhotoshopSaveOptions();
    psdSaveOption.embedColorProfile = true;
    app.activeDocument.saveAs(img_file, psdSaveOption, true, Extension.LOWERCASE);
    ps_doc.close();
    
    app.displayDialogs = DialogModes.ALL;
}