gnome-pomodoro: 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/gnome-pomodoro - from package: gnome-shell-pomodoro

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

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