uwsgi_curl_cron: command not found

Have You tried accessing the binary with the full path?

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_curl_cron - from package: uwsgi-plugin-curl-cron

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