我在 Dell T5600 计算机上运行 16.04 LTS (upstart)。当我尝试升级到 18.04 LTS 时，出现以下问题：
pm@T5600U:~$ sudo do-release-upgrade
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://us.archive.ubuntu.com/ubuntu xenial InRelease
Hit http://packages.microsoft.com/repos/vscode stable InRelease
Get:1 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease [109 kB]
Ign http://dl.google.com/linux/chrome/deb stable InRelease
Get:2 http://us.archive.ubuntu.com/ubuntu xenial-backports InRelease [107 kB]
Get:3 http://security.ubuntu.com/ubuntu xenial-security InRelease [109 kB]
Hit http://dl.google.com/linux/chrome/deb stable Release
Fetched 325 kB in 0s (0 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
Restoring original system state
Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done
pm@T5600U:~$
我究竟做错了什么？