cannot install iOS 7.1 simulator for Xcode 6 (weird file mounting error) I have XCode 5.1 working without problems with iOS 7.1 simulators until yesterday when I upgraded to Xcode 6, the installation was completed successfully, but whenever I try to download and install iOS 7.1 simulator from Preferences -&gt; Downloads, it gives me this weird message:

Could not download and install iOS 7.1 Simulator. Failed to mount  file:///Users/myusername/Library/Caches/com.apple.dt.Xcode/Downloads/Xcode.SDK.iPhoneSimulator.7.1-7.1.dmg at file:///var/folders/f8/4wmmmwj17_96v9jp7h1f4gqc0000gn/T/attached-image-85355a6e6ed97fd1899b8ef3a6052181e745b5fb/: image not recognized


I searched for such error but couldn't find any clue to solve it.
I completely removed XCode using CleanMyMac 2 app, restarted the machine, re-installed Xcode from MAC App Store, the installation was successful, restarted the machine again, and then tried to install iOS 7.1 simulator but to no avail.
Quit Xcode (Command ⌘+Q).
Delete the ~/Library/Caches/com.apple.dt.Xcode folder.
Reopen Xcode.