virtual catalog do_open(const string& name,
const locale& loc) const;The protected member function endeavors to open a message catalog whose name is name. It may make use of the
locale loc in doing so. It returns a value that compares less than zero on failure. Otherwise, the returned value can be
used as the first argument on a later call to get. It should in any case be used as the argument on a later call to close.
In this implementation, the function always returns zero.