do-release-upgrade crashed with TypeError in commit(): wait_for_child() takes 1 positional argument but 2 were given

[Franklin Soares]

during upgrade

ProblemType: Crash
DistroRelease: Ubuntu 15.04
Package: ubuntu-release-upgrader-core 1:15.04.8
ProcVersionSignature: Ubuntu 3.18.0-13.14-generic 3.18.5
Uname: Linux 3.18.0-13-generic x86_64
ApportVersion: 2.16.1-0ubuntu2
Architecture: amd64
CrashCounter: 1
CrashDB: ubuntu
Date: Tue Feb 24 10:34:06 2015
ExecutablePath: /usr/bin/do-release-upgrade
InstallationDate: Installed on 2014-11-20 (96 days ago)
InstallationMedia: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
InterpreterPath: /usr/bin/python3.4
PackageArchitecture: all
ProcCmdline: /usr/bin/python3 /usr/lib/ubuntu-release-upgrader/do-partial-upgrade --frontend=DistUpgradeViewGtk3
PythonArgs: ['/usr/bin/do-release-upgrade', '--frontend=DistUpgradeViewGtk3']
SourcePackage: ubuntu-release-upgrader
Title: do-release-upgrade crashed with TypeError in commit(): wait_for_child() takes 1 positional argument but 2 were given
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

VarLogDistupgradeTermlog:

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.