Improve stack traces for jitted code

kernel/modelverse_kernel/request_handler.py

@@ -66,7 +66,7 @@ class RequestHandler(object):
         # (generator_stack index, [(exception type, handler function)])
         # tuples.
         self.exception_handlers = []
-        self.produce_stack_trace = False
+        self.produce_stack_trace = True
         self.handlers = {
             'CALL' : self.execute_call,
             'CALL_ARGS' : self.execute_call_args,
@@ -237,6 +237,9 @@ class RequestHandler(object):
             except UnwindStackException:
                 # Find out where the exception was thrown.
                 _, _, exc_traceback = sys.exc_info()
+                while exc_traceback.tb_next is not None:
+                    exc_traceback = exc_traceback.tb_next
+
                 line_number = exc_traceback.tb_lineno
                 source_map = top_entry.source_map
                 if source_map is not None: