qmllint: 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/qmllint - from package: qt5-qtdeclarative-devel
/usr/lib64/qt5/bin/qmllint - from package: qt5-qtdeclarative-devel
/usr/lib/qt5/bin/qmllint - from package: qt5-qtdeclarative-devel

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

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