manpage-alert: 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/manpage-alert - from package: rpmdevtools

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

On Debian possible default full paths are:

/usr/bin/manpage-alert - from package: devscripts

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

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