我正在尝试将 Ubuntu 更新到 20.04，但每次执行时它都会中止
$ sudo do-release-upgrade
输出是：
$ sudo do-release-upgrade
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 ...
Fetched 64,4 kB in 0s (0 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
Checking for installed …