我尝试使用以下命令：
sudo apt-get install nessus
但它显示：
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package nessus 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
However the following packages replace it:
openvas-client:i386 openvas-client
E: Package 'nessus' has no installation candidate
现在做什么？