The servers for wmflabs.org zone are:

$ dig +short NS wmflabs.org
labs-ns1.wikimedia.org.
labs-ns0.wikimedia.org.
$

Querying an A record for bastion.wmflabs.org give us no answer:

$ dig bastion.wmflabs.org. @labs-ns1.wikimedia.org

; <<>> DiG 9.7.3-P3 <<>> bastion.wmflabs.org @labs-ns1.wikimedia.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 10575
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;bastion.wmflabs.org. IN A

;; Query time: 465 msec
;; SERVER: 208.80.154.19#53(208.80.154.19)
;; WHEN: Thu Oct 11 15:02:09 2012
;; MSG SIZE rcvd: 37

Same happens for other entries such as integration.wmflabs.org.

Version: unspecified
Severity: major