[Pierre-Marie Baty]

I believe there is no need to put HPB_Bot commands in the bot config file, since the bot config file is read by the bot itself and not the game DLL. Hence you can try something like this:
-----------------------------
#add 6 bots using the default skill level (a random skin will be chosen)
bot_strafe_percent 10
addbot

bot_strafe_percent 20
addbot
----------------------------
This should add you 2 bots in game. The "HPB_Bot" prefix is only needed when you type commands in the server console, not in the config file.