def handle_user_exception(self, e):
        """This method is called whenever an exception occurs that should be
        handled.  A special case are
        :class:`~werkzeug.exception.HTTPException`\s which are forwarded by
        this function to the :meth:`handle_http_exception` method.  This
        function will either return a response value or reraise the
        exception with the same traceback.

        .. versionadded:: 0.7
        """
        exc_type, exc_value, tb = sys.exc_info()
        assert exc_value is e

        # ensure not to trash sys.exc_info() at that point in case someone
        # wants the traceback preserved in handle_http_exception.  Of course
        # we cannot prevent users from trashing it themselves in a custom
        # trap_http_exception method so that's their fault then.
        if isinstance(e, HTTPException) and not self.trap_http_exception(e):
            return self.handle_http_exception(e)

        blueprint_handlers = ()
        handlers = self.error_handler_spec.get(request.blueprint)
        if handlers is not None:
            blueprint_handlers = handlers.get(None, ())
        app_handlers = self.error_handler_spec[None].get(None, ())
        for typecheck, handler in chain(blueprint_handlers, app_handlers):
            if isinstance(e, typecheck):
                return handler(e)

        reraise(exc_type, exc_value, tb)