markdown_py: 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

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/markdown_py - from package: python-markdown

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