5xx errors when hitting weird sub-sub-domains

Hitting https://sx-baidu.cn.godbolt.org/robots.txt (and ignoring the security errors about the cert being invalid) :

```502 ERROR
The request could not be satisfied.
CloudFront wasn't able to connect to the origin.
If you received this error while trying to use an app or access a website, please contact the provider or website owner for assistance.
If you provide content to customers through CloudFront, you can find steps to troubleshoot and help prevent this error by following steps in the CloudFront documentation (https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/http-502-bad-gateway.html).
Generated by cloudfront (CloudFront)
Request ID: MhicKumuYWTtnlclqom4565kF2jWfWo_2fk3Wg16RJ-MFqpnP2OVBg==```

A spam of these just caused a "5xx error rate" SMS alert.