An unresolvable problem occurred while calculating the upgrade.

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'.

oem1@oem1-ThinkPad-T430:~$ ubuntu-bug ubuntu-release-upgrader-core
Gtk-Message: 06:49:17.732: GtkDialog mapped without a transient parent. This is discouraged.
comm: /var/log/dmesg: No such file or directory
oem1@oem1-ThinkPad-T430:~$
(/usr/lib/firefox/firefox:13444): dconf-WARNING **: 06:53:48.085: Unable to open /var/lib/snapd/desktop/dconf/profile/user: Permission denied

oem1@oem1-ThinkPad-T430:~$ lsb_release -rd
Description: Ubuntu 18.04.2 LTS
Release: 18.04
oem1@oem1-ThinkPad-T430:~$ apt-cache policy pkgname
N: Unable to locate package pkgname
oem1@oem1-ThinkPad-T430:~$

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: gnome-terminal 3.28.2-1ubuntu1~18.04.1
ProcVersionSignature: Ubuntu 4.18.0-23.24~18.04.1-generic 4.18.20
Uname: Linux 4.18.0-23-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.6
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Wed Jul 3 07:14:49 2019
ExecutablePath: /usr/lib/gnome-terminal/gnome-terminal-server
InstallationDate: Installed on 2019-06-09 (23 days ago)
InstallationMedia: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 XDG_RUNTIME_DIR=<set>
SourcePackage: gnome-terminal
UpgradeStatus: Upgraded to bionic on 2019-07-03 (0 days ago)