uwsgi_emperor_pg: 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/uwsgi_emperor_pg - from package: uwsgi-plugin-emperor-pg

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

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