Broccoli Compile Error

app.scss

@import "vendor/bootstrap-sass/vendor/assets/stylesheets/bootstrap.scss";

@import "includes/colors";

@import "includes/general";

@import "includes/components/login";

@import "includes/components/controls";

@import "includes/pages/login";

@import "includes/pages/userProfile";

@import "includes/pages/options";

@import "includes/pages/users";

@import "includes/pages/fieldset_layout";

BrocFile.js

  var filterTemplates = require('broccoli-template');
  var uglifyJavaScript = require('broccoli-uglify-js');
  var compileES6 = require('broccoli-es6-concatenator');
//  var compileLess = require('broccoli-less');
  var compileSass = require('broccoli-sass');
  var pickFiles = require('broccoli-static-compiler');
  var mergeTrees = require('broccoli-merge-trees');
  var findBowerTrees = require('broccoli-bower');
  var env = require('broccoli-env').getEnv();

  function preprocess (tree) {
    tree = filterTemplates(tree, {
      extensions: ['hbs', 'handlebars'],
      compileFunction: 'Ember.Handlebars.compile'
    });
    return tree;
  }

  var app = 'app';
  app = pickFiles(app, {
    srcDir: '/',
    destDir: 'appkit' // move under appkit namespace
  });
  app = preprocess(app);

  var styles = 'app/styles';
  styles = pickFiles(styles, {
    srcDir: '/',
    destDir: 'appkit'
  });
  styles = preprocess(styles);

//  var tests = broccoli.makeTree('tests')
//  tests = pickFiles(tests, {
//    srcDir: '/',
//    destDir: 'appkit/tests'
//  })
//  tests = preprocess(tests)

  var vendor = 'vendor';

  var sourceTrees = [app, styles, vendor];
//  if (env !== 'production') {
//    sourceTrees.push(tests)
//  }

  sourceTrees = sourceTrees.concat(findBowerTrees());

  var appAndDependencies = new mergeTrees(sourceTrees, {overwrite: true});

  var appJs = compileES6(appAndDependencies, {
    loaderFile: 'loader/loader.js',
    ignoredModules: [
      'ember/resolver'
    ],
    inputFiles: [
      'appkit/**/*.js'
    ],
    legacyFilesToAppend: [
        (env === 'production' ? 'appkit/config/production.js' : 'appkit/config/development.js'),
        'jquery/dist/jquery.js',
        'handlebars/handlebars.js',
        'ember/ember.js',
        'ember-data/ember-data.js',
        'ember-resolver/dist/ember-resolver.js',
        "bootstrap/dist/js/bootstrap.js",
        "ember-addons.bs_for_ember/dist/js/bs-core.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-alert.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-badge.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-basic.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-button.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-growl-notifications.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-items-action-bar.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-label.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-list-group.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-modal.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-nav.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-notifications.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-progressbar.max.js",
        "ember-addons.bs_for_ember/dist/js/bs-wizard.max.js",
        "ember-validations/index.js",
        "momentjs/moment.js",
        "bootstrap-multiselect/js/bootstrap-multiselect.js",
        "bootstrap-datepicker/js/bootstrap-datepicker.js",
        "redactor/redactor/redactor.js",
        "bootstrap-switch/dist/js/bootstrap-switch.js",
        "jquery.scrollTo/jquery.scrollTo.js",
        "autoNumeric/autoNumeric.js",
        "select2/select2.js"
    ],
    wrapInEval: env !== 'production',
    outputFile: '/assets/app.js'
  })

//  var appCss = compileLess(styles, {paths: ['app.less', 'bootstrap.less', './appkit/includes/'], filename: 'app.css'});
  var appCss = compileSass(sourceTrees, "appkit/styles/app.scss", "assets/app.css");

  var vendorCss = pickFiles(appAndDependencies, {
      srcDir: '/',
      files: ['**/*.css'],
      destDir: '/assets'
  });

  if (env === 'production') {
    appJs = uglifyJavaScript(appJs, {
//      mangle: false,
//      compress: false
    })
  }

  var publicFiles = 'public';
  module.exports = mergeTrees([appJs, appCss, vendorCss, publicFiles]);

Error Output

  Error: EEXIST, file already exists 'tmp/main_file_picker-tmp_dest_dir-ffFiU3QA.tmp/_alerts.scss'
    at Object.fs.openSync (fs.js:427:18)
    at Object.fs.writeFileSync (fs.js:966:15)
    at Object.copyPreserveSync (/LDSG_SVN/Infrastructure/LRT_Ember/node_modules/broccoli-bower/node_modules/broccoli-kitchen-sink-helpers/index.js:140:8)
    at MainFilePicker.write (/LDSG_SVN/Infrastructure/LRT_Ember/node_modules/broccoli-bower/index.js:30:15)
    at MainFilePicker.Writer.read (/LDSG_SVN/Infrastructure/LRT_Ember/node_modules/broccoli-bower/node_modules/broccoli-writer/index.js:11:31)
    at readTree (/LDSG_SVN/Infrastructure/LRT_Ember/node_modules/broccoli/lib/builder.js:61:20)
    at promise.then.then.results.(anonymous function) (/LDSG_SVN/Infrastructure/LRT_Ember/node_modules/broccoli-merge-trees/node_modules/promise-map-series/index.js:8:27)
    at invokeCallback (/LDSG_SVN/Infrastructure/LRT_Ember/node_modules/broccoli-merge-trees/node_modules/promise-map-series/node_modules/rsvp/dist/commonjs/rsvp/promise.js:228:21)
    at publish (/LDSG_SVN/Infrastructure/LRT_Ember/node_modules/broccoli-merge-trees/node_modules/promise-map-series/node_modules/rsvp/dist/commonjs/rsvp/promise.js:176:9)
    at publishFulfillment (/LDSG_SVN/Infrastructure/LRT_Ember/node_modules/broccoli-merge-trees/node_modules/promise-map-series/node_modules/rsvp/dist/commonjs/rsvp/promise.js:312:5)