How to read the status of the Power-LED (or the rainbow square - if you like that better) on Raspberry Pi 3 to detect an low-voltage-condition in a python script? Since the wiring of the Power-LED has changed since Raspberry Pi 2, it seems that GPIO 35 cannot longer be used for that purpose.

Update:
Since it seems to be non-trivial to detect a low-power-condition in code on Raspberry Pi 3, i solved it with a quick hardware hack. I soldered a wire between the Output of the APX803 (the power-monitoring device used on Pi 3) and GPIO26 and that way I can simply read GPIO26 to get the power status. Works like a charm.
Because of Pi3's BT/wifi support Power LED is controlled directly from the GPU through a GPIO expander. 
I believe that there's no way to do what you want
How to read the status of the Power-LED on Raspberry Pi 3 with Python