code: protected void createFailHandler(final String failHandler) {
          if (failHandler == null) {
              _failHandler = DEFAULT_FAIL_HANDLER;
          }
          else {
              _failHandler = createFailHandlerFromString(failHandler);
          }
      }
docs: Convenience method assigning a {@link FailHandler} instance to this kafka spout. If the configured value is
  {@code null}, {@link ConfigUtils#DEFAULT_FAIL_HANDLER} will be used, otherwise the creation is delegated to
  {@link ConfigUtils#createFailHandlerFromString(String)}.
  
  @param failHandler The configuration value for the failure policy.