pychecker: 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/pychecker - from package: pychecker

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

On Debian possible default full paths are:

/usr/bin/pychecker - from package: pychecker

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

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