copr: 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/copr - from package: copr-cli

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

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