xmlpretty: 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 CentOS possible default full paths are:

/usr/bin/xmlpretty - from package: perl-XML-Handler-YAWriter

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/xmlpretty - from package: libxml-handler-yawriter-perl

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

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