Propagate sys.exit(code) up the call stack to the shell

SystemExitException is instantiated and thrown by Base::Interpreter
whenever the python interpreter executes a sys.exit(<exitCode>) call.
However, in the current implementation, the SystemExitException
effectively swallows the <exitCode> hence under this change,
SystemExitException has been extended to save the <exitCode> passed to
the sys.exit() call when it is instantiated and provides a new
getExitCode() accessor method to retrieve the <exitCode> in a
try/catch block.  MainGui.cpp was change to pass the corresponding
<exitCode> to the system exit() call so it is accessible in the shell.

src/Base/Interpreter.cpp

@@ -92,13 +92,46 @@ void PyException::ReportException (void) const
 
 SystemExitException::SystemExitException()
 {
-    _sErrMsg = "System exit";
+    // Set exception message and code based upon the pthon sys.exit() code and/or message 
+    // based upon the the following sys.exit() call semantics.
+    //
+    // Invocation       |  _exitCode  |  _sErrMsg
+    // ---------------- +  ---------  +  --------
+    // sys.exit(int#)   |   int#      |   "System Exit"
+    // sys.exit(string) |   1         |   string
+    // sys.exit()       |   1         |   "System Exit"
+
+    long int errCode = 1;
+    std::string errMsg  = "System exit";
+    PyObject  *type, *value, *traceback, *code;
+
+    PyErr_Fetch(&type, &value, &traceback);
+    PyErr_NormalizeException(&type, &value, &traceback);
+
+    code = PyObject_GetAttrString(value, "code");
+    if (code != NULL && value != Py_None) {
+       Py_DECREF(value);
+       value = code;
+    }
+
+    if (PyInt_Check(value)) {
+        errCode = PyInt_AsLong(value);
+    }
+    else {
+        const char *str = PyString_AsString(value);
+        if (str)
+            errMsg = errMsg + ": " + str;
+    }
+
+    _sErrMsg  = errMsg;
+    _exitCode = errCode;
 }
 
 SystemExitException::SystemExitException(const SystemExitException &inst)
         : Exception(inst)
 {
 }
+
 
 // ---------------------------------------------------------
 

src/Base/Interpreter.h

@@ -87,6 +87,10 @@ public:
     SystemExitException(void);
     SystemExitException(const SystemExitException &inst);
     virtual ~SystemExitException() throw() {}
+    const long getExitCode(void) const { return _exitCode;}
+
+protected:
+    long int _exitCode;
 };
 
 /** If the application starts we release immediately the global interpreter lock

src/Main/MainGui.cpp

@@ -236,8 +236,8 @@ int main( int argc, char ** argv )
         else
             App::Application::runApplication();
     }
-    catch (const Base::SystemExitException&) {
-        exit(0);
+    catch (const Base::SystemExitException& e) {
+        exit(e.getExitCode());
     }
     catch (const Base::Exception& e) {
         e.ReportException();