do-release-upgrade fails to calculate upgrade due to ubuntu-toolchain PPA

[David A. Desrosiers]

Get:66 http://us.archive.ubuntu.com/ubuntu bionic-backports/universe amd64 DEP-11 Metadata [5,100 B]
Get:67 http://us.archive.ubuntu.com/ubuntu bionic-backports/universe DEP-11 64x64 Icons [1,789 B]
Fetched 76.8 MB in 6s (1,564 kB/s)

(appstreamcli:29485): GLib-CRITICAL **: g_strchug: assertion 'string != NULL' failed

(appstreamcli:29485): GLib-CRITICAL **: g_strchomp: assertion 'string != NULL' failed

(appstreamcli:29485): GLib-CRITICAL **: g_strchug: assertion 'string != NULL' failed

(appstreamcli:29485): GLib-CRITICAL **: g_strchomp: assertion 'string != NULL' failed

(appstreamcli:29485): GLib-CRITICAL **: g_strchug: assertion 'string != NULL' failed

(appstreamcli:29485): GLib-CRITICAL **: g_strchomp: assertion 'string != NULL' failed

(appstreamcli:29485): GLib-CRITICAL **: g_strchug: assertion 'string != NULL' failed

(appstreamcli:29485): GLib-CRITICAL **: g_strchomp: assertion 'string != NULL' failed

(appstreamcli:29485): GLib-CRITICAL **: g_strchug: assertion 'string != NULL' failed

(appstreamcli:29485): GLib-CRITICAL **: g_strchomp: assertion 'string != NULL' failed
AppStream cache update completed, but some metadata was ignored due to errors.

Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done

Calculating the changes

Calculating the changes

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader-core 1:16.04.25
ProcVersionSignature: Ubuntu 4.4.0-45.66-generic 4.4.21
Uname: Linux 4.4.0-45-generic x86_64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: XFCE
Date: Wed Jul 25 13:53:15 2018
InstallationDate: Installed on 2016-10-24 (638 days ago)
InstallationMedia: Ubuntu-Server 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.3)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2018-07-25 (0 days ago)

[Brian Murray (brian-murray)]

You have quite a few PPAs enabled and they can cause release upgrades to fail as they may provide package versions which are greater than those in the Ubuntu archive. One PPA which stands out to me is the ubuntu-toolchain PPA - you can try disabling it and removing its packages using the tool 'ppa-purge' from the package of the same name. After that please try the upgrade again.

[Launchpad Janitor (janitor)]

[Expired for ubuntu-release-upgrader (Ubuntu) because there has been no activity for 60 days.]