title: Android Execution failed for task app:proguardRelease
body: <p>I am unable to generate a signed APK for my app, I am stuck with the error java.io.IOException Execution failed for task:'app:proguardRelease' I have what I think is a basic gradle file see below</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
      compileSdkVersion 21
      buildToolsVersion "21.1.1"
  
      defaultConfig {
          applicationId "com.okason.clients"
          minSdkVersion 16
          targetSdkVersion 21
          versionCode 1
          versionName "1.0"
      }
      buildTypes {
          release {
              minifyEnabled true
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
          }
      }
  }
  
  dependencies {
      compile fileTree(dir: 'libs', include: ['*.jar'])
      compile 'com.google.api-client:google-api-client:1.19.0'
      compile 'com.google.android.gms:play-services:6.1.71'
      compile 'com.android.support:support-v4:21.0.0'
      compile 'com.android.support:appcompat-v7:21.0.0'
  }
  </code></pre>
  
  <p>The generated Proguard-rules.pro file is empty amd I have not touched the proguard-android.txt file in the SDK. I even tried to copy this file to the root of app to be the same location as the app.gradle file without success. </p>
  
  <p>I tried to run this command gradlew.bat assembleRelease per this <code>[SO Question][1]</code> with success. Please can someone take a look and let me know what I am doing wrong. I have update the SDK and Android Studio to the latest versions.</p>