tidy_changelog: 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/tidy_changelog - from package: libcpan-changes-perl

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

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