It was rather trivial to add the error message, here is how:
in uglify-js module, added a error reporting log to the file lib\parse.js in following method:
function js_error(message, filename, line, col, pos) { console.log(message, filename, line, col, pos); throw new JS_Parse_Error(message, filename, line, col, pos); };Looks like the error handling of fault barrier doesn't do what it supposed to.
@PitaJ Thank again for your help.