无法定位软件包monodevelop

安装Altman的时候，需要monodevelop，安装时提示无法定位，以下为解决方法：

1. 将软件包添加至存储库中

sudo apt install apt-transport-https dirmngr gnupg ca-certificates
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
echo "deb https://download.mono-project.com/repo/debian preview-stretch main" | sudo tee /etc/apt/sources.list.d/mono-official-preview.list
sudo apt update

2.安装mono

sudo apt-get install mono-devel mono-complete monodevelop