How can I configure the plugin to notify only on errors?

Question

gulp.js

How to configure notify so that notifications appear only on errors?
"gulp-notify": "^3.0.0" - installed
notify = require("gulp-notify") - enabled
What should I add to this task?

gulp.task('sass', function(){ // Создаем таск "sass"
    return gulp.src(['app/sass/*.sass',
                     'app/libs/libs.sass']) // Берем источник
       	.pipe(sass({
          includePaths: bourbon.includePaths
          }))
        .pipe(gulp.dest('app/css')) // Выгружаем результата в папку app/css
        .pipe(browserSync.reload({stream: true})) // Обновляем CSS на странице при изменении
     });