old_contents: import gulp from 'gulp';
  import eslint from 'gulp-eslint';
  import plumber from 'gulp-plumber';
  
  gulp.task('lint', () =>
    gulp.src('src/**/*.js')
      .pipe(plumber({
        errorHandler: error => {
          console.error(`[task] eslint ${error.plugin}\n${error.message}`);
        }
      }))
      .pipe(eslint({ useEslintrc: true }))
      .pipe(eslint.format())
      .pipe(eslint.failOnError())
      .pipe(plumber.stop())
  );
  
new_contents: import gulp from 'gulp';
  import eslint from 'gulp-eslint';
  import plumber from 'gulp-plumber';
  
  gulp.task('lint', () =>
    gulp.src([
      'src/**/*.js',
      'gulpfile.babel.js',
      'gulp/**/*.js',
      'config/**/*.js',
    ])
      .pipe(plumber({
        errorHandler: error => {
          console.error(`[task] eslint ${error.plugin}\n${error.message}`);
        }
      }))
      .pipe(eslint({ useEslintrc: true }))
      .pipe(eslint.format())
      .pipe(eslint.failOnError())
      .pipe(plumber.stop())
  );
  
subject: add lint targets