dipy_quickbundles: command not found

Have You tried accessing the binary with the full path?

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/dipy_quickbundles - from package: python-dipy

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