Cannot download packages

I see this problem from time to time.

Cannot download this url for example;

Is this some server/mirror failing?

$ curl -I ""
HTTP/1.1 404 Not Found
Date: Tue, 12 Sep 2017 17:26:05 GMT
Server: Apache
Strict-Transport-Security: max-age=31536000; includeSubDomains
Content-Type: text/html; charset=iso-8859-1
Via: 1.1 (Apache/2.4.10)
Moved to archive, read corresponding topic here on forum.