whups-svn-hook: 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/whups-svn-hook - from package: php-horde-whups

You may install the required package with command apt-get install {package}
Error in other languages:
whups-svn-hook: bevel nie gevind nie
whups-svn-hook: comandă negăsită
whups-svn-hook: comando não encontrado
whups-svn-hook: commande introuvable
whups-svn-hook: command not found
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whups-svn-hook: không tìm thấy lệnh
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whups-svn-hook: Kommando nicht gefunden.
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whups-svn-hook: nie znaleziono polecenia
whups-svn-hook: níor aimsíodh an t-ordú
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whups-svn-hook: perintah tidak ditemukan
whups-svn-hook: príkaz nenájdený
whups-svn-hook: příkaz nenalezen
whups-svn-hook: команда не найдена
whups-svn-hook: командата не е открита
whups-svn-hook: 命令找不到
whups-svn-hook: コマンドが見つかりません