code: public static String getRequiredSystemProperty(String propertyName, String errorMsgIfNotFound) {
          String propertyValue = System.getProperty(propertyName);
          if (propertyValue == null) {
              throw new RuntimeException(errorMsgIfNotFound);
          }
          return propertyValue;
      }
docs: Retrieve system property by name, failing if it's not found
  
  @param propertyName
  @param errorMsgIfNotFound
  @return Value of property if it exists