title: Gradle Build failed with ProGuard enabled, missing classes.jar
body: <p>I'm getting the following error when trying to build a signed APK with ProGuard enabled:</p>
  
  <blockquote>
    <p>Error:Execution failed for task ':app:packageRelease'.
    Unable to compute hash of D:\Work\Android\MyApp\app\build\intermediates\classes-proguard\release\classes.jar</p>
  </blockquote>
  
  <p>I checked the path given, and there is no classes.jar file. Where can I get the .jar from?</p>