install crashes with ValueError: invalid literal for int() with base 10: ''

[Anthony Di Franco]

Installer crashes just after progress tracking of package installation begins.

from /var/log/syslog:

Sep 28 05:02:59 ubuntu-gnome ubiquity[5631]: debconffilter_done: ubi-usersetup (current: ubi-usersetup)
Sep 28 05:02:59 ubuntu-gnome ubiquity[5631]: Step_before = stepUserInfo
Sep 28 05:03:00 ubuntu-gnome kernel: [ 514.135712] traps: ubiquity[5631] trap int3 ip:7f6b539b7a6b sp:7ffef3c06880 error:0
Sep 28 05:03:13 ubuntu-gnome ubiquity.desktop[5622]: Trace/breakpoint trap (core dumped)
Sep 28 05:03:13 ubuntu-gnome ubiquity: Traceback (most recent call last):
Sep 28 05:03:13 ubuntu-gnome ubiquity: File "/usr/share/ubiquity/plugininstall.py", line 1776, in <module>
Sep 28 05:03:13 ubuntu-gnome ubiquity: install = Install()
Sep 28 05:03:13 ubuntu-gnome ubiquity: File "/usr/share/ubiquity/plugininstall.py", line 137, in __init__
Sep 28 05:03:13 ubuntu-gnome ubiquity: if self.db.get('base-installer/install-recommends') == 'false':
Sep 28 05:03:13 ubuntu-gnome ubiquity: File "/usr/lib/python3/dist-packages/debconf.py", line 62, in <lambda>
Sep 28 05:03:13 ubuntu-gnome ubiquity: lambda *args, **kw: self.command(command, *args, **kw))
Sep 28 05:03:13 ubuntu-gnome ubiquity: File "/usr/lib/python3/dist-packages/debconf.py", line 83, in command
Sep 28 05:03:13 ubuntu-gnome ubiquity: status = int(status)
Sep 28 05:03:13 ubuntu-gnome ubiquity: ValueError: invalid literal for int() with base 10: ''
Sep 28 05:04:46 ubuntu-gnome AptDaemon: INFO: Quitting due to inactivity
Sep 28 05:04:46 ubuntu-gnome AptDaemon: INFO: Quitting was requested
Sep 28 05:04:46 ubuntu-gnome org.freedesktop.PackageKit[4345]: 22:04:46 AptDaemon [INFO]: Quitting due to inactivity
Sep 28 05:04:46 ubuntu-gnome org.freedesktop.PackageKit[4345]: 22:04:46 AptDaemon [INFO]: Quitting was requested
Sep 28 05:09:42 ubuntu-gnome systemd[1]: Starting Cleanup of Temporary Directories...
Sep 28 05:09:42 ubuntu-gnome systemd-tmpfiles[26530]: [/usr/lib/tmpfiles.d/var.conf:14] Duplicate line for path "/var/log", ignoring.
Sep 28 05:09:42 ubuntu-gnome systemd[1]: Started Cleanup of Temporary Directories.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63.2
ProcVersionSignature: Ubuntu 4.4.0-31.50-generic 4.4.13
Uname: Linux 4.4.0-31-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CasperVersion: 1.376
CurrentDesktop: GNOME
Date: Tue Sep 27 22:47:46 2016
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu-gnome.seed boot=casper quiet splash ---
LiveMediaBuild: Ubuntu-GNOME 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160720)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)