occlusion_query: 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/lib64/piglit/bin/occlusion_query - from package: piglit

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

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