private boolean outputIsError(String output) {
    if (output == null) {
      return false;
    }
    boolean error = false;
    for (final String errorOutput : ERROR_OUTPUTS) {
      error = output.indexOf(errorOutput) > -1;
      if (error) {
        return error;
      }
    }
    return error;
  }
Returns <code>true</code> if the <code>output</code> string contains a known error message.
geode-core/src/main/java/org/apache/geode/admin/internal/EnabledManagedEntityController.java