CentOS 7 iso download fails

[olberger]

The rebuild of CentOS 7 fails:

    virtualbox-iso: Error downloading: Error making HTTP GET request: 404 Not Found
==> virtualbox-iso: ISO download failed.
Build 'virtualbox-iso' errored: ISO download failed.

I guess a later update than 7.6.1810 is now needed

[olberger]

It seems that changing the path in iso_url in centos7-*.json to http://archive.kernel.org/centos-vault/7.6.1810/isos/x86_64/CentOS-7-x86_64-DVD-1810.iso should do it