dh_quilt_unpatch: 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_quilt_unpatch - from package: quilt

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

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