twitter-to-xhtml: 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/twitter-to-xhtml - from package: python-twitter

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

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