xmlindent: 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/xmlindent - from package: xmlindent

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

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