anchor.diff:  
     try {
       _ApkBuilder builder = new _ApkBuilder(androidSdk.latestVersion);
  +    String error = builder.checkDependencies();
  +    if (error != null) {
  +      printError(error);
  +      return 1;
  +    }
   
       File classesDex = new File('${tempDir.path}/classes.dex');
       builder.compileClassesDex(classesDex, components.jars);
  
positive.code:     _jarsigner = os.which('jarsigner');
    }
  
    void compileClassesDex(File classesDex, List<File> jars) {
      List<String> packageArgs = <String>[_dx.path,
        '--dex',
  
negative.code:   }
  
    void sign(File keystore, String keystorePassword, String keyAlias, String keyPassword, File outputApk) {
      assert(_jarsigner != null);
      runCheckedSync(<String>[_jarsigner.path,
        '-keystore', keystore.path,
        '-storepass', keystorePassword,
  