Warning C4101 unreferenced local variable

[zfengyan]

Line 732 ->:

catch(const std::exception &e){
        return false;
      }

the parameter e is not used, thus MSVC may give a warning.

solution:

catch(const std::exception &e){
        std::cerr << "exception caught: " << e.what() << '\n';
        return false;
      }