3.1.3 upgrade Let's Encrypt no longer works.
I upgraded two servers, one at a time to 3.1.3. After upgrading the first I was no longer able to use Let's Encrypt to set up SSL on a new site.
Second server after upgrade I un-ticked Let's encrypt and SSL, let it finish its business then re-ticked Let's Encrypt and it failed.
Server 1 Ubuntu 14.04.5 using latest certbot-auto in /opt/certbot
Server 2 Debian Wheezy using certbot-auto in /opt/certbot
Both servers worked properly prior to ispconfig upgrade.
Server 1 seems to be trying to use IPv6 to resolve letsencrypt.org domain.
From syslog:
May 17 07:29:08 edison named[1108]: error (network unreachable) resolving 'letsencrypt.org/DS/IN': 2001:503:ba3e::2:30#53 May 17 07:29:08 edison named[1108]: error (network unreachable) resolving 'letsencrypt.org/DS/IN': 2001:500:b::1#53 May 17 07:29:08 edison named[1108]: error (network unreachable) resolving 'letsencrypt.org/DS/IN': 2001:500:c::1#53 May 17 08:02:58 edison named[1108]: error (network unreachable) resolving 'letsencrypt.org/DS/IN': 2001:500:f::1#53 May 17 09:03:01 edison named[1108]: error (network unreachable) resolving 'ocsp.int-x3.letsencrypt.org/AAAA/IN': 2001:500:e::1#53 May 17 09:03:01 edison named[1108]: error (network unreachable) resolving 'ocsp.int-x3.letsencrypt.org/A/IN': 2001:500:e::1#53 May 17 09:25:22 edison named[1108]: error (network unreachable) resolving 'ocsp.int-x3.letsencrypt.org/AAAA/IN': 2600:1401:2::10#53 May 17 09:25:22 edison named[1108]: error (network unreachable) resolving 'ocsp.int-x3.letsencrypt.org/A/IN': 2600:1401:2::10#53 May 17 09:25:22 edison named[1108]: error (network unreachable) resolving 'ocsp.int-x3.letsencrypt.org/AAAA/IN': 2a02:26f0:67::42#53 May 17 09:25:22 edison named[1108]: error (network unreachable) resolving 'ocsp.int-x3.letsencrypt.org/A/IN': 2a02:26f0:67::42#53 May 17 09:25:22 edison named[1108]: error (network unreachable) resolving 'ocsp.int-x3.letsencrypt.org.edgesuite.net/A/IN': 2600:1401:2::2#53 May 17 09:25:22 edison named[1108]: error (network unreachable) resolving 'ocsp.int-x3.letsencrypt.org.edgesuite.net/AAAA/IN': 2600:1401:2::2#53 May 17 09:25:22 edison named[1108]: error (network unreachable) resolving 'ocsp.int-x3.letsencrypt.org.edgesuite.net/A/IN': 2600:1401:1::40#53 May 17 09:25:22 edison named[1108]: error (network unreachable) resolving 'ocsp.int-x3.letsencrypt.org.edgesuite.net/AAAA/IN': 2600:1401:1::40#53