@RequestedDeletion, surprised you saw that kind of failure. I just tried it on a fresh 9.1 test VM, and it's working fine. Notably, this VM doesn't have the EPEL repo configured at all--the letsencrypt client docs say it needs to be enabled for CentOS 6, and it's present (though disabled) on my main server. I wondered if the letsencrypt-auto script might have enabled it anyway, but that does not appear to have been the case. The only repo added was scl-python27, and the only packages added to the base install (before running letsencrypt-auto) were scl-utils and python27 (plus whatever dependencies it pulled in with it).