Callback error handling improvements:

- print traceback
- don't use fprintf()
- clear exception (implied by PyErr_Print())

Mac/Modules/drag/_Dragmodule.c

@@ -898,7 +898,8 @@ dragglue_TrackingHandler(DragTrackingMessage theMessage, WindowPtr theWindow,
 	rv = PyEval_CallObject((PyObject *)handlerRefCon, args);
 	Py_DECREF(args);
 	if ( rv == NULL ) {
-		fprintf(stderr, "Drag: Exception in TrackingHandler\n");
+		PySys_WriteStderr("Drag: Exception in TrackingHandler\n");
+		PyErr_Print();
 		return -1;
 	}
 	i = -1;
@@ -923,7 +924,8 @@ dragglue_ReceiveHandler(WindowPtr theWindow, void *handlerRefCon,
 	rv = PyEval_CallObject((PyObject *)handlerRefCon, args);
 	Py_DECREF(args);
 	if ( rv == NULL ) {
-		fprintf(stderr, "Drag: Exception in ReceiveHandler\n");
+		PySys_WriteStderr("Drag: Exception in ReceiveHandler\n");
+		PyErr_Print();
 		return -1;
 	}
 	i = -1;
@@ -951,7 +953,8 @@ dragglue_SendData(FlavorType theType, void *dragSendRefCon,
 	rv = PyEval_CallObject(self->sendproc, args);
 	Py_DECREF(args);
 	if ( rv == NULL ) {
-		fprintf(stderr, "Drag: Exception in SendDataHandler\n");
+		PySys_WriteStderr("Drag: Exception in SendDataHandler\n");
+		PyErr_Print();
 		return -1;
 	}
 	i = -1;

Mac/Modules/drag/dragsupport.py

@@ -82,7 +82,8 @@ dragglue_TrackingHandler(DragTrackingMessage theMessage, WindowPtr theWindow,
 	rv = PyEval_CallObject((PyObject *)handlerRefCon, args);
 	Py_DECREF(args);
 	if ( rv == NULL ) {
-		fprintf(stderr, "Drag: Exception in TrackingHandler\\n");
+		PySys_WriteStderr("Drag: Exception in TrackingHandler\\n");
+		PyErr_Print();
 		return -1;
 	}
 	i = -1;
@@ -107,7 +108,8 @@ dragglue_ReceiveHandler(WindowPtr theWindow, void *handlerRefCon,
 	rv = PyEval_CallObject((PyObject *)handlerRefCon, args);
 	Py_DECREF(args);
 	if ( rv == NULL ) {
-		fprintf(stderr, "Drag: Exception in ReceiveHandler\\n");
+		PySys_WriteStderr("Drag: Exception in ReceiveHandler\\n");
+		PyErr_Print();
 		return -1;
 	}
 	i = -1;
@@ -135,7 +137,8 @@ dragglue_SendData(FlavorType theType, void *dragSendRefCon,
 	rv = PyEval_CallObject(self->sendproc, args);
 	Py_DECREF(args);
 	if ( rv == NULL ) {
-		fprintf(stderr, "Drag: Exception in SendDataHandler\\n");
+		PySys_WriteStderr("Drag: Exception in SendDataHandler\\n");
+		PyErr_Print();
 		return -1;
 	}
 	i = -1;