Reported by Klocwork #151.

v2 can be NULL if exception2 is NULL.  I don't think that condition can happen,
but I'm not sure it can't either.  Now the code will protect against either
being NULL.

Python/pythonrun.c

@@ -1064,6 +1064,17 @@ PyErr_PrintEx(int set_sys_last_vars)
 			}
 			PyErr_Fetch(&exception2, &v2, &tb2);
 			PyErr_NormalizeException(&exception2, &v2, &tb2);
+			/* It should not be possible for exception2 or v2
+			   to be NULL. However PyErr_Display() can't
+			   tolerate NULLs, so just be safe. */
+			if (exception2 == NULL) {
+				exception2 = Py_None;
+				Py_INCREF(exception2);
+			}
+			if (v2 == NULL) {
+				v2 = Py_None;
+				Py_INCREF(v2);
+			}
 			if (Py_FlushLine())
 				PyErr_Clear();
 			fflush(stdout);
@@ -1071,8 +1082,8 @@ PyErr_PrintEx(int set_sys_last_vars)
 			PyErr_Display(exception2, v2, tb2);
 			PySys_WriteStderr("\nOriginal exception was:\n");
 			PyErr_Display(exception, v, tb);
-			Py_XDECREF(exception2);
-			Py_XDECREF(v2);
+			Py_DECREF(exception2);
+			Py_DECREF(v2);
 			Py_XDECREF(tb2);
 		}
 		Py_XDECREF(result);