Exception handling middleware for aiohttp (python 3.5)

exception_middleware.py

def json_error(status_code: int, exception: Exception) -> web.Response:
    """
    Returns a Response from an exception.
    Used for error middleware.
    :param status_code:
    :param exception:
    :return:
    """
    return web.Response(
        status=status_code,
        body=json.dumps({
            'error': exception.__class__.__name__,
            'detail': str(exception)
        }).encode('utf-8'),
        content_type='application/json')


async def error_middleware(app: web.Application, handler):
    """
    This middleware handles with exceptions received from views or previous middleware.

    :param app:
    :param handler:
    :return:
    """
    async def middleware_handler(request):
        try:
            response = await handler(request)
            if response.status == 404:
                return json_error(response.status, Exception(response.message))
            return response
        except web.HTTPException as ex:
            if ex.status == 404:
                return json_error(ex.status, ex)
            raise
        except Exception as e:
            logger.warning('Request {} has failed with exception: {}'.format(request, repr(e)))
            return json_error(500, e)

    return middleware_handler




app = web.Application(middlewares=[error_middleware])