title: Execution failed for task ':app:transformClassesAndResourcesWithProguardForRelease' Android
body: <p>I am building an app in Android, this is the build.gradle file:</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
      compileSdkVersion 25
      buildToolsVersion "25.0.1"
      defaultConfig {
          applicationId "myApp"
          minSdkVersion 21
          targetSdkVersion 25
          versionCode 1
          versionName "1.0"
          testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
          multiDexEnabled true
      }
      buildTypes {
          release {
              minifyEnabled true
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
          }
      }
      packagingOptions {
          packagingOptions {
              exclude 'META-INF/DEPENDENCIES.txt'
              exclude 'META-INF/LICENSE.txt'
              exclude 'META-INF/NOTICE.txt'
              exclude 'META-INF/NOTICE'
              exclude 'META-INF/LICENSE'
              exclude 'META-INF/DEPENDENCIES'
              exclude 'META-INF/notice.txt'
              exclude 'META-INF/license.txt'
              exclude 'META-INF/dependencies.txt'
              exclude 'META-INF/LGPL2.1'
          }
      }
  }
  
  dependencies {
      compile fileTree(dir: 'libs', include: ['*.jar'])
      androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
          exclude group: 'com.android.support', module: 'support-annotations'
      })
      compile project(':geth')
      compile 'com.android.volley:volley:1.0.0'
      compile 'com.google.android.gms:play-services-maps:10.0.1'
      compile 'com.android.support:appcompat-v7:25.1.0'
      compile 'com.android.support:support-v4:25.1.0'
      compile 'com.android.support:design:25.1.0'
      compile 'com.android.support:multidex:1.0.1'
      compile 'org.web3j:core-android:1.1.0'
      testCompile 'junit:junit:4.12'
  }
  </code></pre>
  
  <p>When I try to build my app, I get the following warnings which result to a failed build:</p>
  
  <p><a href="http://pastebin.com/EhMr66Yg" rel="nofollow noreferrer">http://pastebin.com/EhMr66Yg</a></p>
  
  <p>Should I add -dontwarn rules for these warnings? What causes them?</p>
  
  <p>Does the build fail because of the 67 warnings or because of the last one:</p>
  
  <p>"there were 1 unresolved references to library class members.
           You probably need to update the library versions."</p>
  
  <p>Thanks.</p>