dh_installyorick: 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/dh_installyorick - from package: yorick-dev

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

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