unable to upgrade to 20.04 from 18.04

[Philip Lo]

Unable to upgrade to 20.04 LTS from 18.04 LTS

Description: Ubuntu 18.04.5 LTS
Release: 18.04

philip@philip-ThinkPad-T520:/var/log/dist-upgrade$ sudo do-release-upgrade
[sudo] password for philip:
Checking for a new Ubuntu release
Get:1 Upgrade tool signature [1,554 B]
Get:2 Upgrade tool [1,342 kB]
Fetched 1,344 kB in 0s (0 B/s)
authenticate 'focal.tar.gz' against 'focal.tar.gz.gpg'
extracting 'focal.tar.gz'

Reading cache

Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Hit http://ca.archive.ubuntu.com/ubuntu bionic InRelease
Get:1 http://ca.archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:2 http://ca.archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Get:3 http://security.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]
Hit http://archive.canonical.com/ubuntu bionic InRelease
Get:4 http://ca.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [1,089 kB]
Get:5 http://ca.archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages [748 kB]
Fetched 2,089 kB in 0s (0 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done

Updating repository information
Hit http://ca.archive.ubuntu.com/ubuntu focal InRelease
Hit http://archive.canonical.com/ubuntu focal InRelease
Get:1 http://ca.archive.ubuntu.com/ubuntu focal-updates InRelease [111 kB]
Get:2 http://security.ubuntu.com/ubuntu focal-security InRelease [107 kB]
Get:3 http://ca.archive.ubuntu.com/ubuntu focal-backports InRelease [98.3 kB]
Fetched 317 kB in 0s (0 B/s)

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 18.04
Package: ubuntu-release-upgrader-core 1:18.04.38
ProcVersionSignature: Ubuntu 4.15.0-118.119-generic 4.15.18
Uname: Linux 4.15.0-118-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.17
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Tue Sep 29 00:51:09 2020
InstallationDate: Installed on 2018-10-13 (717 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_CA.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-09-29 (0 days ago)