从 Ubuntu 19.04 更新到 Ubuntu 19.10 后，我刚刚尝试安装 TortoiseHg，我得到了以下信息：
sudo apt install tortoisehg
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package tortoisehg is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'tortoisehg' has no installation candidate
目前是否有任何安装 TortoiseHg 的选项，除了我自己从源代码构建它？
关于可能重复安装 TortoiseHg 的评论：需要更高的 Mercurial 版本- 它不能解决问题。
目前我正在使用 mercurial 版本4.8.2，这是 19.10 中最新可用的版本，没有添加 mercurial-ppa。
当我尝试添加 mercurial-ppa 时，出现以下错误：
sudo add-apt-repository ppa:mercurial-ppa/releases
See https://launchpad.net/~mercurial-ppa
More info: https://launchpad.net/~mercurial-ppa/+archive/ubuntu/releases
Press [ENTER] to continue or Ctrl-c to cancel adding it.
Ign:1 http://ppa.launchpad.net/mercurial-ppa/releases/ubuntu eoan InRelease
Err:2 http://ppa.launchpad.net/mercurial-ppa/releases/ubuntu eoan Release
404 Not Found [IP: 91.189.95.83 80]
Hit:3 http://security.ubuntu.com/ubuntu eoan-security InRelease
Hit:4 http://nl.archive.ubuntu.com/ubuntu eoan InRelease
Hit:5 http://nl.archive.ubuntu.com/ubuntu eoan-updates InRelease
Hit:6 https://repo.skype.com/deb stable InRelease
Hit:7 http://nl.archive.ubuntu.com/ubuntu eoan-backports InRelease
Ign:8 http://dl.google.com/linux/chrome/deb stable InRelease
Ign:9 http://dl.google.com/linux/earth/deb stable InRelease
Hit:10 http://dl.google.com/linux/chrome/deb stable Release
Hit:11 http://dl.google.com/linux/earth/deb stable Release
Hit:12 https://dl.winehq.org/wine-builds/ubuntu eoan InRelease
Reading package lists... Done
E: The repository 'http://ppa.launchpad.net/mercurial-ppa/releases/ubuntu eoan Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.