dh_aspell-simple: 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/dh_aspell-simple - from package: dictionaries-common-dev

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

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