nghttp: 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 Debian possible default full paths are:

/usr/bin/nghttp - from package: nghttp2

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

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