xml-resolver: 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/xml-resolver - from package: xml-commons-resolver

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

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