Base: set sys.last_vars to enable post mortem debugging after exception

* Update Interpreter.cpp to enable stack trace

This enables python debuggers to stack trace after an exception.
See https://forum.freecad.org/viewtopic.php?p=714349#p714349

Co-authored-by: bdieterm <119257544+bdieterm@users.noreply.github.com>

src/Base/Interpreter.cpp

@@ -125,6 +125,8 @@ void PyException::ReportException () const
 {
     if (!_isReported) {
         _isReported = true;
+        // set sys.last_vars to make post-mortem debugging work
+        PySys_SetObject("last_traceback", PP_last_traceback);
         Base::Console().DeveloperError("pyException","%s%s: %s\n",
             _stackTrace.c_str(), _errorType.c_str(), what());
     }