Okay. I tried this:

if key == '67336':
os.system("dbus-send --type=signal --session /com/nokia/hildon_desktop com.nokia.hildon_desktop.close_window_time int32:-1")

It did not work. I replaced '67336' with "bksp/backspace" and finally with '@' (through fn-space, longpressing does not seem to work in task manager) and it works fine, so no problems with the script, only the key. I wonder why.

I want to try to bind "kp_return/enter" for something as well, not sure if it would work, now that backspace fails.