copr-cli: 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-cli - from package: copr-cli

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

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