我正在尝试下载一些软件包进行离线安装apt-get download，但由于某种原因，apt-rdepends包括不存在的软件包。这是我正在使用的命令：
apt-get download $(apt-rdepends libboost1.55-all-dev | grep -v "^ ")
这是我得到的输出：
E: Can't select candidate version from package libstdc++-dev as it has no candidate
E: Can't select candidate version from package debconf-2.0 as it has no candidate
E: Can't select candidate version from package libc-dev as it has no candidate
E: Can't select candidate version from package python-celementtree as it has no candidate
E: Can't select candidate version from package python-elementtree as it has no …