An unresolvable problem occurred while calculating the upgrade.

[Akul Sahariya]

Checking for a new Ubuntu release
Get:1 Upgrade tool signature [819 B]
Get:2 Upgrade tool [1,246 kB]
Fetched 1,247 kB in 0s (0 B/s)
authenticate 'bionic.tar.gz' against 'bionic.tar.gz.gpg'
extracting 'bionic.tar.gz'

Reading cache

Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Hit http://archive.canonical.com/ubuntu xenial InRelease
Fetched 0 B in 0s (0 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done

Updating repository information
Get:1 http://archive.canonical.com/ubuntu bionic InRelease [10.2 kB]
Get:2 http://archive.ubuntu.com/ubuntu bionic InRelease [242 kB]
Get:3 http://archive.canonical.com/ubuntu bionic/partner amd64 Packages [2,304 B]
Get:4 http://archive.canonical.com/ubuntu bionic/partner i386 Packages [2,300 B]
Get:5 http://archive.canonical.com/ubuntu bionic/partner Translation-en [1,272 B]
Get:6 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages [1,019 kB]
Get:7 http://archive.ubuntu.com/ubuntu bionic/main i386 Packages [1,007 kB]
Get:8 http://archive.ubuntu.com/ubuntu bionic/main Translation-en [516 kB]
Get:9 http://archive.ubuntu.com/ubuntu bionic/main amd64 DEP-11 Metadata [477 kB]
Get:10 http://archive.ubuntu.com/ubuntu bionic/main DEP-11 64x64 Icons [245 kB]
Fetched 3,522 kB in 0s (0 B/s)

(appstreamcli:15830): GLib-CRITICAL **: g_strchug: assertion 'string != NULL' failed

(appstreamcli:15830): GLib-CRITICAL **: g_strchomp: assertion 'string != NULL' failed

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.

If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.If
you want to investigate this yourself the log files in
'/var/log/dist-upgrade' will contain details about the upgrade.
Specifically, look at 'main.log' and 'apt.log'.

Restoring original system state

Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader-core 1:16.04.26 [origin: unknown]
ProcVersionSignature: Ubuntu 4.4.0-142.168-generic 4.4.167
Uname: Linux 4.4.0-142-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Sun Feb 17 22:06:04 2019
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-xenial-amd64-20160624-2
InstallationDate: Installed on 2018-01-25 (388 days ago)
InstallationMedia: Ubuntu 16.04 "Xenial" - Build amd64 LIVE Binary 20160624-10:47
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2019-02-17 (0 days ago)
mtime.conffile..etc.update-manager.release-upgrades: 2019-02-17T19:43:46.418347

[Launchpad Janitor (janitor)]

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