Implements the mapper's WSGI interface.

def wsgi(self, environ, start_response):
        """Implements the mapper's WSGI interface."""
        request = Request(environ)
        ctx = Context(request)
        try:
            try:
                response = self(request, ctx)
                ctx._run_callbacks('finalize', (request, response))
                response = response.conditional_to(request)
            except HTTPException as e:
                response = e.response
            except Exception:
                self.handle_error(request, ctx)
                response = InternalServerError().response

            response.add_callback(lambda: ctx._run_callbacks('close'))
            return response(environ, start_response)
        finally:
            ctx._run_callbacks('teardown', log_errors=True)