pep8: 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/pep8 - from package: python-pep8

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

On Debian possible default full paths are:

/usr/bin/pep8 - from package: pep8

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

Error in other languages:
pep8: bevel nie gevind nie
pep8: comandă negăsită
pep8: comando não encontrado
pep8: commande introuvable
pep8: command not found
pep8: käsku ei ole
pep8: không tìm thấy lệnh
pep8: komanda nerasta
pep8: Kommando nicht gefunden.
pep8: kommandot finns inte
pep8: komut yok
pep8: nie znaleziono polecenia
pep8: níor aimsíodh an t-ordú
pep8: no se encontró la orden
pep8: no s'ha trobat l'ordre
pep8: opdracht niet gevonden
pep8: parancs nem található
pep8: perintah tidak ditemukan
pep8: príkaz nenájdený
pep8: příkaz nenalezen
pep8: команда не найдена
pep8: командата не е открита
pep8: 命令找不到
pep8: コマンドが見つかりません