title: When I run gulp, unexpected error pops up(event.js : 160)
body: <p>Here is the snapshot of command prompt when I run gulp. Previously it used to work correctly but now, it is showing some weird errors. 
  <a href="https://i.stack.imgur.com/LauOD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/LauOD.png" alt="command prompt&#39;s snapshot"></a></p>
  
  <p>my view folder is supposed to contain only templates, so why is it displaying bootstrap.social.css not found?</p>
  
  <p>and my project folder looks like-</p>
  
  <pre><code>Project-
     app-
         fonts-...
         images-...
         scripts-
                 app.js
                 controllers.js
                 services.js
         styles-...
         index.html
         views-
               various html templates
      bower_components-...
      dist-..
      node_modules-...
      gulpfile.js
      package.json
     ...
  </code></pre>
  
  <p>here is my gulpfile.js' code:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var gulp = require('gulp'),
      minifycss = require('gulp-minify-css'),
      jshint = require('gulp-jshint'),
      stylish = require('jshint-stylish'),
      uglify = require('gulp-uglify'),
      usemin = require('gulp-usemin'),
      imagemin = require('gulp-imagemin'),
      rename = require('gulp-rename'),
      concat = require('gulp-concat'),
      notify = require('gulp-notify'),
      cache = require('gulp-cache'),
      changed = require('gulp-changed'),
      rev = require('gulp-rev'),
      browserSync = require('browser-sync'),
      ngannotate = require('gulp-ng-annotate'),
      del = require('del');
  
      gulp.task('jshint', function() {
        return gulp.src('app/scripts/**/*.js')
        .pipe(jshint())
        .pipe(jshint.reporter(stylish));
      });
  
      // Clean
      gulp.task('clean', function() {
          return del(['dist']);
      });
  
      // Default task
      gulp.task('default', ['clean'], function() {
          gulp.start('usemin', 'imagemin','copyfonts');
      });
      gulp.task('usemin',['jshint'], function () {
    return gulp.src('./app/**/*.html')
        .pipe(usemin({
          css:[minifycss(),rev()],
          js: [ngannotate(),uglify(),rev()]
        }))
        .pipe(gulp.dest('dist/'));
  });
  
  // Images
  gulp.task('imagemin', function() {
    return del(['dist/images']), gulp.src('app/images/**/*')
      .pipe(cache(imagemin({ optimizationLevel: 3, progressive: true, interlaced: true })))
      .pipe(gulp.dest('dist/images'))
      .pipe(notify({ message: 'Images task complete' }));
  });
  
  gulp.task('copyfonts', ['clean'], function() {
     gulp.src('./bower_components/font-awesome/fonts/**/*.{ttf,woff,eof,svg}*')
     .pipe(gulp.dest('./dist/fonts'));
     gulp.src('./bower_components/bootstrap/dist/fonts/**/*.{ttf,woff,eof,svg}*')
     .pipe(gulp.dest('./dist/fonts'));
  });
  // Watch
  gulp.task('watch', ['browser-sync'], function() {
    // Watch .js files
    gulp.watch('{app/scripts/**/*.js,app/styles/**/*.css,app/**/*.html}', ['usemin']);
        // Watch image files
    gulp.watch('app/images/**/*', ['imagemin']);
  
  });
  
  gulp.task('browser-sync', ['default'], function () {
     var files = [
        'app/**/*.html',
        'app/styles/**/*.css',
        'app/images/**/*.png',
        'app/scripts/**/*.js',
        'dist/**/*'
     ];
  
     browserSync.init(files, {
        server: {
           baseDir: "dist",
           index: "index.html"
        }
     });
          // Watch any files in dist/, reload on change
    gulp.watch(['dist/**']).on('change', browserSync.reload);
      });</code></pre>
  </div>
  </div>
  </p>