xml_spellcheck: 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_spellcheck - from package: perl-XML-Twig

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

On Debian possible default full paths are:

/usr/bin/xml_spellcheck - from package: xml-twig-tools

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

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