xmlsort: 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/xmlsort - from package: libxml-filter-sort-perl

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

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