anchor.diff:            String cask = createDarteditorCask(cask_class_name, url, release_revision, md5, isRawCsAvailable, installSection);
             File outputFile = new File(outputDirectory.path + '/' + cask_file_name);
             return outputFile.create(recursive: true)
  -              .then((file) => outputFile.writeAsString(cask));
  +            .then((file) {
  +            outputFile.writeAsString(cask);
  +            return null;
  +          });
           }
           else
           {
  
positive.code:         String cask = createDarteditorCask(cask_class_name, url, release_revision, md5, isRawCsAvailable, installSection);
          File outputFile = new File(outputDirectory.path + '/' + cask_file_name);
          return outputFile.create(recursive: true)
              .then((file) => outputFile.writeAsString(cask));
        });
  }
  
  
negative.code:         return getAsString(Uri.parse(md5_file_url), client);
        })
        .then((String body) {
          if (body == null) return null;
          md5 = md5_regex.firstMatch(body).group(1);
  
          return getAsString(Uri.parse(cs_md5_file_url), client);
        })
        .then((String body) {
          if (body == null) return null;
          cs_md5 = md5_regex.firstMatch(body).group(1);
          int revision = int.parse(release_revision);
          isRawCsAvailable = cs_md5 != "xml";
  