cons: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/cons - from package: cons

You may install the required package with command apt-get install {package}

Error in other languages:
cons: bevel nie gevind nie
cons: comandă negăsită
cons: comando não encontrado
cons: commande introuvable
cons: command not found
cons: käsku ei ole
cons: không tìm thấy lệnh
cons: komanda nerasta
cons: Kommando nicht gefunden.
cons: kommandot finns inte
cons: komut yok
cons: nie znaleziono polecenia
cons: níor aimsíodh an t-ordú
cons: no se encontró la orden
cons: no s'ha trobat l'ordre
cons: opdracht niet gevonden
cons: parancs nem található
cons: perintah tidak ditemukan
cons: príkaz nenájdený
cons: příkaz nenalezen
cons: команда не найдена
cons: командата не е открита
cons: 命令找不到
cons: コマンドが見つかりません