It appears that the test host (sha256.tbs-internet.com) used by test_algorithms in test_ssl.py no longer exists.

It was showing up as a certificate failure in the test because it ended up falling back to a resolv.conf search path which yielded a host that did do SSL but obviously with the wrong certificate.

db3l@buildbot-ubuntu:~$ host sha256.tbs-internet.com
Host sha256.tbs-internet.com not found: 3(NXDOMAIN)

db3l@buildbot-ubuntu:~/tmp/python3.x/Lib/test$ dig +short ns tbs-internet.com
NS1.tbs-internet.com.
maj.pitux.com.
ns2.atdynet.com.
nsc.pitux.com.
db3l@buildbot-ubuntu:~/tmp/python3.x/Lib/test$ dig @ns1.tbs-internet.com sha256.tbs-internet.com

; <<>> DiG 9.9.5-3ubuntu0.5-Ubuntu <<>> @ns1.tbs-internet.com sha256.tbs-internet.com
; (2 servers found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 25154
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;sha256.tbs-internet.com.	IN	A

;; AUTHORITY SECTION:
tbs-internet.com.	3600	IN	SOA	ovh12.tbs-internet.com. hostmaster.tbs-internet.com. 2015110705 21600 3600 2419200 3600

;; Query time: 93 msec
;; SERVER: 2001:41d0:8:380d::1#53(2001:41d0:8:380d::1)
;; WHEN: Thu Nov 19 16:51:58 EST 2015
;; MSG SIZE  rcvd: 105


What I can't yet understand is why this is not causing issues on other slaves.  I suppose some might be skipping the test if SNI was not supported, but surely not all of them?

Ah, it appears that the transient_internet context manager in the test causes it to be skipped if the host is unknown.  So mine was just "lucky" in that it fell back to connecting somewhere else.

I've removed my resolver search path on bolen-ubuntu which will resolve the test failures on that slave, but I presume test_algorithms is never being run by anyone at this point.

So the mystery of that buildbot is solved, but I think that test needs some work.

The sha256.tbs-internet.com has been down for a while and the DNS record is no longer available. Alex and I agreed that the test no longer makes sense, too. RSA certs with SHA-256 signatures are de-facto standard and supported by OpenSSL for a long time. We test SHA-256 certs with several other tests that talk to remote servers.

I'm going to remove the test and sha256 cert.

New changeset 002d64039b60c1a9289f981fe73a5cf91d082136 by Christian Heimes in branch 'master':
bpo-25674: remove sha256.tbs-internet.com ssl test (#3297)
https://github.com/python/cpython/commit/002d64039b60c1a9289f981fe73a5cf91d082136

New changeset 4bc8ef0eeed191f9398a90e748f732cfba67546d by Christian Heimes in branch '3.6':
[3.6] bpo-25674: remove sha256.tbs-internet.com ssl test (GH-3297) (#3300)
https://github.com/python/cpython/commit/4bc8ef0eeed191f9398a90e748f732cfba67546d

New changeset 57d963b0b559078ca419811d0d25fea27d42f30c by Christian Heimes in branch '2.7':
[2.7] bpo-25674: remove sha256.tbs-internet.com ssl test (GH-3297) (#3301)
https://github.com/python/cpython/commit/57d963b0b559078ca419811d0d25fea27d42f30c

I've removed the sha256.tbs-internet.com from 2.7, 3.6, and master. 3.5 and previous versions are in security fix-only mode.