I have been previously installed Preenv request but I deleted by mistake, now I want to install again. I do so:
step X Terminal and write
sudo gainroot (enter) OK
apt-get install preenv (enter) and it gives me this message Xterminal
Reading package lists ... done
Building Dependency Tree
Reading state information ... Done
Preenv Package is not available, butt is referred to by Another package.
May this mean That the package is missing, Has Been obsoleted, or
Another is onely Available from source.
E: Package Preenv encountered on installation candidate

This is the message that gives the X Terminal.

Very very very please, can someone help