title: Gulp command stops with Error: spawn ENOTDIR
body: <p><em>I recognize that there are many similar questions, but none with a solution that I can find.</em></p>
  
  <p>I am trying to compile Sass and JS but am getting the following error:</p>
  
  <pre><code>Error: spawn ENOTDIR
      at exports._errnoException (util.js:746:11)
      at ChildProcess.spawn (child_process.js:1162:11)
      at exports.spawn (child_process.js:995:9)
      ... and so on...
  </code></pre>
  
  <p>It appears that the choke point is the <code>return sass(...)</code> statement. My <code>gulpfile.js</code> looks like this:</p>
  
  <pre><code>var gulp        = require('gulp'),
      sass        = require('gulp-ruby-sass'),
      notify      = require('gulp-notify'),
      autoprefix  = require('gulp-autoprefixer'),
      source_sass = 'assets/sass/',
      target_css  = 'public/css/',
      source_js   = 'assets/js/',
      target_js   = 'public/js/';
  
  gulp.task('css', function () {
      return sass(source_sass + 'main.scss', {style: 'compressed'})
          .pipe(autoprefix('last 10 version'))
          .pipe(gulp.dest(target_css))
          .pipe(notify('CSS processed.'));
  });
  
  gulp.task('js', function () {
      return gulp.src(source_js + '**/*.js')
          .pipe(gulp.dest(target_js))
          .pipe(notify('JS processed.'));
  });
  
  gulp.task('watch', function () {
      gulp.watch(source_sass + '**/*.scss', ['css']);
      gulp.watch(source_js + '**/*.js', ['js']);
  });
  
  gulp.task('default', ['css', 'js', 'watch']);
  </code></pre>
  
  <ul>
  <li>OS X Yosemite 10.10.3</li>
  <li>Ruby v2.0.0p481</li>
  <li>Gem v2.0.14</li>
  <li>Node v0.12.3</li>
  <li>NPM v2.9.1</li>
  <li>Gulp v3.8.11</li>
  </ul>