There is 2 packages for that :
1 - '''command-not-found''' that is the old one used, the output is something
like this :
$ gdit
No command 'gdit' found, did you mean:
Command 'edit' from package 'mime-support' (main)
Command 'gedit' from package 'gedit' (main)
Command 'gdis' from package 'gdis' (universe)
Command 'git' from package 'git' (main)
2 - '''auto-apt''' it is the new one, the output is something like this :
"gparted" was not found.
The program 'gparted' is currently not installed. You can install it by
typing:
sudo apt-get install gparted
I'm not using trisquel right know so I can't say which of those 2 is
available in Trisquel. But, at least, '''command-not-found''' should be
available in the repositories.
I hope this helped.