ndg_httpclient: 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/ndg_httpclient - from package: python2-ndg_httpsclient

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

On Debian possible default full paths are:

/usr/bin/ndg_httpclient - from package: python-ndg-httpsclient

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

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