I cannot upgrade to ubuntu 18.04.
Here is the output of
$ sudo do-release-upgrade
Checking for a new Ubuntu release
Get:1 Upgrade tool signature [819 B]
Get:2 Upgrade tool [1,258 kB]
Fetched 1,259 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
Ign http://linux.dropbox.com/ubuntu wily InRelease
Hit http://ch.archive.ubuntu.com/ubuntu xenial InRelease
Hit http://ppa.launchpad.net/octave/stable/ubuntu xenial InRelease
Hit http://linux.dropbox.com/ubuntu wily Release
Get:1 http://security.ubuntu.com/ubuntu xenial-security InRelease [107 kB]
Hit https://repo.skype.com/deb stable InRelease
Hit http://ch.archive.ubuntu.com/ubuntu xenial-updates InRelease
Hit http://repo.acestream.org/ubuntu trusty InRelease
Hit http://ch.archive.ubuntu.com/ubuntu xenial-backports InRelease
Hit http://ppa.launchpad.net/samoilov-lex/aftl-stable/ubuntu xenial InRelease
Hit http://ppa.launchpad.net/team-xbmc/ppa/ubuntu xenial InRelease
Hit http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu xenial InRelease
Fetched 107 kB in 0s (0 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
Updating repository information
Third party sources disabled
Some third party entries in your sources.list were disabled. You can
re-enable them after the upgrade with the 'software-properties' tool
or your package manager.
To continue please press [ENTER]
Get:1 http://security.ubuntu.com/ubuntu bionic-security InRelease [83.2 kB]
Get:2 http://ch.archive.ubuntu.com/ubuntu bionic InRelease [242 kB]
Get:3 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages [168 kB]
Get:4 http://ch.archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:5 http://ch.archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Get:6 http://security.ubuntu.com/ubuntu bionic-security/main i386 Packages [134 kB]
Get:7 http://security.ubuntu.com/ubuntu bionic-security/main Translation-en [63.6 kB]
Get:8 http://security.ubuntu.com/ubuntu bionic-security/main amd64 DEP-11 Metadata [204 B]
Get:9 http://security.ubuntu.com/ubuntu bionic-security/main DEP-11 64x64 Icons [29 B]
Get:10 http://security.ubuntu.com/ubuntu bionic-security/universe amd64 Packages [66.8 kB]
Get:11 http://ch.archive.ubuntu.com/ubuntu bionic/main amd64 Packages [1,019 kB]
Get:12 http://security.ubuntu.com/ubuntu bionic-security/universe i386 Packages [66.7 kB]
Get:13 http://security.ubuntu.com/ubuntu bionic-security/universe Translation-en [39.3 kB]
Get:14 http://security.ubuntu.com/ubuntu bionic-security/universe amd64 DEP-11 Metadata [6,820 B]
Get:15 http://security.ubuntu.com/ubuntu bionic-security/universe DEP-11 64x64 Icons [11.3 kB]
Get:16 http://security.ubuntu.com/ubuntu bionic-security/multiverse amd64 Packages [1,444 B]
Get:17 http://security.ubuntu.com/ubuntu bionic-security/multiverse i386 Packages [1,608 B]
Get:18 http://security.ubuntu.com/ubuntu bionic-security/multiverse Translation-en [996 B]
Get:19 http://ch.archive.ubuntu.com/ubuntu bionic/main i386 Packages [1,007 kB]
Get:20 http://ch.archive.ubuntu.com/ubuntu bionic/main Translation-en [516 kB]
Get:21 http://ch.archive.ubuntu.com/ubuntu bionic/main amd64 DEP-11 Metadata [477 kB]
Get:22 http://ch.archive.ubuntu.com/ubuntu bionic/main DEP-11 64x64 Icons [245 kB]
Get:23 http://ch.archive.ubuntu.com/ubuntu bionic/restricted amd64 Packages [9,184 B]
Get:24 http://ch.archive.ubuntu.com/ubuntu bionic/restricted i386 Packages [9,156 B]
Get:25 http://ch.archive.ubuntu.com/ubuntu bionic/restricted Translation-en [3,584 B]
Get:26 http://ch.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages [8,570 kB]
Get:27 http://ch.archive.ubuntu.com/ubuntu bionic/universe i386 Packages [8,531 kB]
Get:28 http://ch.archive.ubuntu.com/ubuntu bionic/universe Translation-en [4,941 kB]
Get:29 http://ch.archive.ubuntu.com/ubuntu bionic/universe amd64 DEP-11 Metadata [3,287 kB]
Get:30 http://ch.archive.ubuntu.com/ubuntu bionic/universe DEP-11 64x64 Icons [8,420 kB]
Get:31 http://ch.archive.ubuntu.com/ubuntu bionic/multiverse amd64 Packages [151 kB]
Get:32 http://ch.archive.ubuntu.com/ubuntu bionic/multiverse i386 Packages [144 kB]
Get:33 http://ch.archive.ubuntu.com/ubuntu bionic/multiverse Translation-en [108 kB]
Get:34 http://ch.archive.ubuntu.com/ubuntu bionic/multiverse amd64 DEP-11 Metadata [49.7 kB]
Get:35 http://ch.archive.ubuntu.com/ubuntu bionic/multiverse DEP-11 64x64 Icons [225 kB]
Get:36 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [328 kB]
Get:37 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages [293 kB]
Get:38 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main Translation-en [125 kB]
Get:39 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main amd64 DEP-11 Metadata [139 kB]
Get:40 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main DEP-11 64x64 Icons [56.9 kB]
Get:41 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages [199 kB]
Get:42 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe i386 Packages [199 kB]
Get:43 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe Translation-en [94.1 kB]
Get:44 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 DEP-11 Metadata [166 kB]
Get:45 http://ch.archive.ubuntu.com/ubuntu bionic-updates/universe DEP-11 64x64 Icons [285 kB]
Get:46 http://ch.archive.ubuntu.com/ubuntu bionic-updates/multiverse amd64 Packages [4,180 B]
Get:47 http://ch.archive.ubuntu.com/ubuntu bionic-updates/multiverse i386 Packages [4,336 B]
Get:48 http://ch.archive.ubuntu.com/ubuntu bionic-updates/multiverse Translation-en [2,740 B]
Get:49 http://ch.archive.ubuntu.com/ubuntu bionic-updates/multiverse amd64 DEP-11 Metadata [2,464 B]
Get:50 http://ch.archive.ubuntu.com/ubuntu bionic-updates/multiverse DEP-11 64x64 Icons [2,638 B]
Get:51 http://ch.archive.ubuntu.com/ubuntu bionic-backports/universe amd64 Packages [2,840 B]
Get:52 http://ch.archive.ubuntu.com/ubuntu bionic-backports/universe i386 Packages [2,832 B]
Get:53 http://ch.archive.ubuntu.com/ubuntu bionic-backports/universe Translation-en [1,200 B]
Get:54 http://ch.archive.ubuntu.com/ubuntu bionic-backports/universe amd64 DEP-11 Metadata [5,100 B]
Get:55 http://ch.archive.ubuntu.com/ubuntu bionic-backports/universe DEP-11 64x64 Icons [1,789 B]
Fetched 40.7 MB in 6s (6,429 kB/s)
(appstreamcli:19472): GLib-CRITICAL **: g_strchug: assertion 'string != NULL' failed
(appstreamcli:19472): GLib-CRITICAL **: g_strchomp: assertion 'string != NULL' failed
(appstreamcli:19472): GLib-CRITICAL **: g_strchug: assertion 'string != NULL' failed
(appstreamcli:19472): GLib-CRITICAL **: g_strchomp: assertion 'string != NULL' failed
(appstreamcli:19472): GLib-CRITICAL **: g_strchug: assertion 'string != NULL' failed
(appstreamcli:19472): 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.
This can be caused by:
* Upgrading to a pre-release version of Ubuntu
* Running the current pre-release version of Ubuntu
* Unofficial software packages not provided by Ubuntu
If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.
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 1:16.04.25
ProcVersionSignature: Ubuntu 4.15.0-34.37~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-34-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Fri Sep 21 10:16:54 2018
InstallationDate: Installed on 2017-06-08 (469 days ago)
InstallationMedia: Ubuntu 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215.2)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2018-09-21 (0 days ago)
