title: Gradle Build Failure
body: <p>My project compiles and executes well on debug mode but when i try to generate a signed apk, errors arise. This appears on the message log:</p>
  
  <pre><code>:app:proguardRelease
  Warning:android.support.v4.app.DialogFragment: can't find referenced class android.support.v4.app.DialogFragment$DialogStyle
  Warning:android.support.v4.app.FragmentTransaction: can't find referenced class android.support.v4.app.FragmentTransaction$Transit
  Warning:android.support.v4.view.ViewCompat: can't find referenced class android.support.v4.view.ViewCompat$ResolvedLayoutDirectionMode
  Warning:android.support.v4.view.ViewCompat: can't find referenced class android.support.v4.view.ViewCompat$LayoutDirectionMode
  Warning:android.support.v4.view.ViewCompat: can't find referenced class android.support.v4.view.ViewCompat$LayerType
  Warning:android.support.v4.view.ViewCompat: can't find referenced class android.support.v4.view.ViewCompat$AccessibilityLiveRegion
  Warning:android.support.v4.view.ViewCompat: can't find referenced class android.support.v4.view.ViewCompat$ImportantForAccessibility
  Warning:android.support.v4.view.ViewCompat: can't find referenced class android.support.v4.view.ViewCompat$OverScroll
  Warning:android.support.v4.widget.DrawerLayout: can't find referenced class android.support.v4.widget.DrawerLayout$EdgeGravity
  Warning:android.support.v4.widget.DrawerLayout: can't find referenced class android.support.v4.widget.DrawerLayout$LockMode
  Warning:android.support.v4.widget.DrawerLayout: can't find referenced class android.support.v4.widget.DrawerLayout$State
  Warning:there were 11 unresolved references to classes or interfaces.
           You may need to add missing library jars or update their versions.
           If your code works fine without the missing classes, you can suppress
           the warnings with '-dontwarn' options.
           (http://proguard.sourceforge.net/manual/troubleshooting.html#unresolvedclass)
  Exception while processing task 
  java.io.IOException: Please correct the above warnings first.
      at proguard.Initializer.execute(Initializer.java:473)
      at proguard.ProGuard.initialize(ProGuard.java:233)
      at proguard.ProGuard.execute(ProGuard.java:98)
      at proguard.gradle.ProGuardTask.proguard(ProGuardTask.java:1074)
      at com.android.build.gradle.tasks.AndroidProGuardTask.doMinification(AndroidProGuardTask.java:139)
      at com.android.build.gradle.tasks.AndroidProGuardTask$1.run(AndroidProGuardTask.java:115)
      at com.android.builder.tasks.Job.runTask(Job.java:48)
      at com.android.build.gradle.tasks.SimpleWorkQueue$EmptyThreadContext.runTask(SimpleWorkQueue.java:41)
      at com.android.builder.tasks.WorkQueue.run(WorkQueue.java:227)
      at java.lang.Thread.run(Thread.java:745)
  :app:dexRelease UP-TO-DATE
  :app:crashlyticsStoreDeobsRelease
  :app:crashlyticsUploadDeobsRelease
  :app:validateExternalOverrideSigning
  :app:packageRelease FAILED
  Error:Execution failed for task ':app:packageRelease'.
  &gt; Unable to compute hash of /home/kombo/RAL/Mpasho/app/build/intermediates/classes-proguard/release/classes.jar
  </code></pre>
  
  <p>I have tried every possible way of remedying this by updating my build tools, using the latest gradle version, checking all the dependencies and the error still shows up.</p>
  
  <p>I am pretty sure the v4 support library is present in the project since no errors arise in debug mode.</p>