Bug#804139: bumblebee: after recent xorg + nvidia updates in sid, "Cannot access secondary GPU - error"

[Nohus]

I am affected by the same bug since I recently upgraded from Debian Jessie to Stretch. Bumblebee worked previously. Now I get this problem, both on nouveau and on non free nvidia drivers.

Here are my logs:

[nohus] nohus:(~)❯❯❯ optirun -vv --debug glxgears
[ 3527.143580] [DEBUG]Reading file: /etc/bumblebee/bumblebee.conf
[ 3527.143825] [DEBUG]optirun version 3.2.1 starting...
[ 3527.143837] [DEBUG]Active configuration:
[ 3527.143844] [DEBUG] bumblebeed config file: /etc/bumblebee/bumblebee.conf
[ 3527.143851] [DEBUG] X display: :8
[ 3527.143858] [DEBUG] LD_LIBRARY_PATH: 
[ 3527.143865] [DEBUG] Socket path: /var/run/bumblebee.socket
[ 3527.143872] [DEBUG] Accel/display bridge: auto
[ 3527.143878] [DEBUG] VGL Compression: proxy
[ 3527.143886] [DEBUG] VGLrun extra options: 
[ 3527.143893] [DEBUG] Primus LD Path: /usr/lib/x86_64-linux-gnu/primus:/usr/lib/i386-linux-gnu/primus:/usr/lib/primus:/usr/lib32/primus
[ 3527.594436] [DEBUG]Using auto-detected bridge virtualgl
[ 3528.051511] [INFO]Response: No - error: [XORG] (EE) 

[ 3528.051551] [ERROR]Cannot access secondary GPU - error: [XORG] (EE) 

[ 3528.051558] [DEBUG]Socket closed.
[ 3528.051573] [ERROR]Aborting because fallback start is disabled.
[ 3528.051579] [DEBUG]Killing all remaining processes.

In journalctl when running optirun:

Dec 31 15:53:14 nohus bumblebeed[719]: [ 4023.682085] [ERROR][XORG] (EE)
Dec 31 15:53:14 nohus bumblebeed[719]: [ 4023.682109] [ERROR][XORG] (EE)
Dec 31 15:53:14 nohus bumblebeed[719]: [ 4023.682116] [ERROR][XORG] (EE)
Dec 31 15:53:14 nohus bumblebeed[719]: [ 4023.682121] [ERROR][XORG] (EE)
Dec 31 15:53:14 nohus bumblebeed[719]: [ 4023.682127] [ERROR][XORG] (EE)
Dec 31 15:53:14 nohus bumblebeed[719]: [ 4023.682133] [ERROR]X did not start properly

Also, the GPU stays ON as reported by /proc/acpi/bbswitch after trying to run optirun, until turned OFF manually with "rmmod nouveau; tee /proc/acpi/bbswitch <<< OFF"