private String getSampleRepositoryData() {
    return "[{\"repositories\":[],\"OperatingSystems/os_type\":\"redhat7\"}]";
  }
@return sample JSON data from repo_version data (no repositories defined) where 'OperatingSystems/ambari_managed_repositories' is missing
ambari-server/src/test/java/org/apache/ambari/server/upgrade/UpgradeCatalog270Test.java