python3-gflags2man: 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/python3-gflags2man - from package: python3-gflags

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

Error in other languages:
python3-gflags2man: bevel nie gevind nie
python3-gflags2man: comandă negăsită
python3-gflags2man: comando não encontrado
python3-gflags2man: commande introuvable
python3-gflags2man: command not found
python3-gflags2man: käsku ei ole
python3-gflags2man: không tìm thấy lệnh
python3-gflags2man: komanda nerasta
python3-gflags2man: Kommando nicht gefunden.
python3-gflags2man: kommandot finns inte
python3-gflags2man: komut yok
python3-gflags2man: nie znaleziono polecenia
python3-gflags2man: níor aimsíodh an t-ordú
python3-gflags2man: no se encontró la orden
python3-gflags2man: no s'ha trobat l'ordre
python3-gflags2man: opdracht niet gevonden
python3-gflags2man: parancs nem található
python3-gflags2man: perintah tidak ditemukan
python3-gflags2man: príkaz nenájdený
python3-gflags2man: příkaz nenalezen
python3-gflags2man: команда не найдена
python3-gflags2man: командата не е открита
python3-gflags2man: 命令找不到
python3-gflags2man: コマンドが見つかりません