handler.pyc: 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/lib/python2.6/site-packages/viewvc/bin/mod_python/handler.pyc - from package: viewvc

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

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