当运行update-manager将 19.04 升级到 19.10 时，我在控制台中得到了这个：
Checking for a new Ubuntu release
Please install all available updates for your release before upgrading.
尝试do-release-upgrade：
$ do-release-upgrade
Checking for a new Ubuntu release
Please install all available updates for your release before upgrading.
所以尝试upgrade：
$ sudo apt-get upgrade
The following packages have been kept back:
libsnmp30
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
事实上，我似乎无法安装任何东西：
$ sudo apt-get install emacs
Reading package lists... …