realpath.py: 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/libexec/TeXmacs/bin/realpath.py - from package: TeXmacs

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

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