title: ProGuard fails when updating to Android SDK 23
body: <p>I am trying to update the <a href="https://github.com/johnjohndoe/Umweltzone" rel="nofollow">Umweltzone Android application</a> to SDK 23. Therefore, I change the project configuration as follows:</p>
  
  <pre class="lang-groovy prettyprint-override"><code>// Excerpt from Umweltzone/build.gradle
  compileSdkVersion 23
  // ...
  compile "com.android.support:design:23.1.1"
  </code></pre>
  
  <p>When I build a <strong>release</strong> version this <strong>fails</strong> with this error (tailing part):</p>
  
  <blockquote>
    <p>...<br>
    Note: there were 3 references to unknown classes.<br>
          You should check your configuration for typos.<br>
          (<a href="http://proguard.sourceforge.net/manual" rel="nofollow">http://proguard.sourceforge.net/manual</a>  /troubleshooting.html#unknownclass)  </p>
    
    <p>Note: there were 2 classes trying to access enclosing classes using
    reflection.<br>
          You should consider keeping the inner classes attributes
          (using '-keepattributes InnerClasses').<br>
          (<a href="http://proguard.sourceforge.net/manual/troubleshooting.html#attributes" rel="nofollow">http://proguard.sourceforge.net/manual/troubleshooting.html#attributes</a>)  </p>
    
    <p>Note: there were 100 unkept descriptor classes in kept class members. 
          You should consider explicitly keeping the mentioned classes
          (using '-keep').<br>
          (<a href="http://proguard.sourceforge.net/manual/troubleshooting.html#descriptorclass" rel="nofollow">http://proguard.sourceforge.net/manual/troubleshooting.html#descriptorclass</a>)  </p>
    
    <p>Note: there were 5 unresolved dynamic references to classes or
    interfaces.<br>
          You should check if you need to specify additional program jars.<br>
          (<a href="http://proguard.sourceforge.net/manual/troubleshooting.html#dynamicalclass" rel="nofollow">http://proguard.sourceforge.net/manual/troubleshooting.html#dynamicalclass</a>)  </p>
    
    <p>Note: there were 3 accesses to class members by means of
    introspection.<br>
          You should consider explicitly keeping the mentioned class members
          (using '-keep' or '-keepclassmembers').<br>
          (<a href="http://proguard.sourceforge.net/manual/troubleshooting.html#dynamicalclassmember" rel="nofollow">http://proguard.sourceforge.net/manual/troubleshooting.html#dynamicalclassmember</a>)  </p>
    
    <p>Warning: there were 1 unresolved references to library class members.<br>
             You probably need to update the library versions.<br>
             (<a href="http://proguard.sourceforge.net/manual/troubleshooting.html#unresolvedlibraryclassmember" rel="nofollow">http://proguard.sourceforge.net/manual/troubleshooting.html#unresolvedlibraryclassmember</a>)  </p>
    
    <p>Warning: Exception while processing task java.io.IOException: Please
    correct the above warnings first.<br>
    :Umweltzone:transformClassesAndResourcesWithProguardForRelease FAILED  </p>
    
    <p>FAILURE: Build failed with an exception.  </p>
    
    <ul>
    <li>What went wrong: Execution failed for task   ':Umweltzone:transformClassesAndResourcesWithProguardForRelease'.<br>
    > java.io.IOException: Please correct the above warnings first.</li>
    </ul>
  </blockquote>
  
  <p>The release build does work with SDK 22. The ProGuard configuration can be found <a href="https://github.com/johnjohndoe/Umweltzone/blob/master/Umweltzone/proguard.cfg" rel="nofollow">here</a>. The full build output can be found <a href="http://pastebin.com/6yaACR6Z" rel="nofollow">here</a> since StackOverflow does not let me paste here because of length restrictions.</p>