pycassaShell: 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 Debian possible default full paths are:

/usr/bin/pycassaShell - from package: python-pycassa

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

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