icupkg: 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/sbin/icupkg - from package: icu

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

On Debian possible default full paths are:

/usr/sbin/icupkg - from package: icu-devtools

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

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