title: NSData writeToFile method returns true but file is not written to the disk
body: <p>I have developed an OS X app and I sometimes need to save some pictures to the disk. I have a method to do that :</p>
  <pre><code>func saveImageAtPath(image: NSImage, path: String)
  {
      if let data = image.TIFFRepresentation
      {
          let bitmap = NSBitmapImageRep(data: data)
          let pngImage = bitmap?.representationUsingType(NSBitmapImageFileType.NSPNGFileType, properties: [:])
          
          NSLog(&quot;Path : %@&quot;, path)
          
          if let _ = pngImage?.writeToFile(path, atomically: false)
          {
              NSLog(&quot;Everything should work...&quot;)
          }
      }
  }
  </code></pre>
  <p>When I try to save an image, everything seems to work, the following text is displayed in the console :</p>
  <blockquote>
  <p>Path :
  /Users/myusername/Documents/Pictures/Apps/testPictures/mypicture.png</p>
  <p>Everything should work...</p>
  </blockquote>
  <p>Everything was working perfectly a month ago.
  Here is my conf :</p>
  <p>OS X Yosemite 10.10.5
  Xcode 7.2</p>
  <p>If anyone has an idea... That'd be great !</p>
  <p>Thanks in advance.</p>