def Proxy(self, status, headers, exc_info=None):
self.call_context['<STR_LIT:status>'] = status<EOL>self.call_context['<STR_LIT>'] = headers<EOL>self.call_context['<STR_LIT>'] = exc_info<EOL>return self.body_buffer.write<EOL>
Save args, defer start_response until response body is parsed.

        Create output buffer for body to be written into.
        Note: this is not quite WSGI compliant: The body should come back as an
          iterator returned from calling service_app() but instead, StartResponse
          returns a writer that will be later called to output the body.
        See google/appengine/ext/webapp/__init__.py::Response.wsgi_write()
            write = start_response('%d %s' % self.__status, self.__wsgi_headers)
            write(body)

        Args:
          status: Http status to be sent with this response
          headers: Http headers to be sent with this response
          exc_info: Exception info to be displayed for this response
        Returns:
          callable that takes as an argument the body content