qvoronoi: 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/qvoronoi - from package: qhull

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

On Debian possible default full paths are:

/usr/bin/qvoronoi - from package: qhull-bin

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

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