xmlrev: command not found

Have You tried accessing the binary with the full path?

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/xmlrev - from package: xmldiff-xmlrev

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