package memtest86+ 5.01-3ubuntu2 hangs on upgrade from 14.04 to xenial

[Luke Faraone]

when attempting to upgrade to xenial, memtest86+'s postinst froze.

(ubuntu)lfaraone@aqua:~$ ps aux | grep do-rel
root 7975 0.0 0.0 54668 3784 pts/3 S+ 16:15 0:00 sudo do-release-upgrade -d
lfaraone 30444 0.0 0.0 14232 964 pts/7 S+ 16:35 0:00 grep do-rel
(ubuntu)lfaraone@aqua:~$ pstree 7975
sudo───screen───screen───xenial─┬─gnome-session-i─┬─{gdbus}
                                │ └─{gmain}
                                ├─sh───sleep
                                ├─xenial───dpkg───frontend───memtest86+.post
                                ├─{gdbus}
                                └─{gmain}
(ubuntu)lfaraone@aqua:~$ ps aux | grep memtest86+.post
root 23919 0.0 0.1 63016 17648 pts/8 S+ 16:31 0:00 /usr/bin/perl -w /usr/share/debconf/frontend /var/lib/dpkg/info/memtest86+.postinst configure 5.01-3ubuntu1
root 23926 0.0 0.0 0 0 pts/8 Z+ 16:31 0:00 [memtest86+.post] <defunct>
lfaraone 31348 0.0 0.0 14232 2620 pts/7 R+ 16:37 0:00 grep memtest86+.post

Looks like its subprocess died but dpkg failed to reap it? (The actual error that triggered apport was me killing the debconf process 23919)

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: memtest86+ 5.01-3ubuntu2
ProcVersionSignature: Ubuntu 4.2.0-35.40-generic 4.2.8-ckt5
Uname: Linux 4.2.0-35-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
Date: Sun Apr 17 16:37:22 2016
ErrorMessage: subprocess installed post-installation script was killed by signal (Terminated)
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1
 apt 1.2.10ubuntu1
SourcePackage: grub2
Title: package memtest86+ 5.01-3ubuntu2 failed to install/upgrade: subprocess installed post-installation script was killed by signal (Terminated)
UpgradeStatus: Upgraded to xenial on 2016-04-17 (0 days ago)