Enforcing usage of Vesa driver for Xorg seems not to work

[Wawrzyniec Niewodniczański]

I try to autoconfigure Ubuntu using pressed. It fails for Xorg. Ubuntu Nouveau drivers are broken for many of our machines (graphic cards), therefore I wants to enforce usage of VESA. I use following line in the pressed conf file:

xserver-xorg xserver-xorg/config/device/driver select vesa

but after installation Ubuntu starts X with Nouveau anyway.

Coutd you please advices the proper pressed command to enforce Vesa drivers?

Part of my pressed related to X.
### X configuration
# X can detect the right driver for some cards, but if you're preseeding,
# you override whatever it chooses. Still, vesa will work most places.
xserver-xorg xserver-xorg/config/device/driver select vesa

# A caveat with mouse autodetection is that if it fails, X will retry it
# over and over. So if it's preseeded to be done, there is a possibility of
# an infinite loop if the mouse is not autodetected.
#xserver-xorg xserver-xorg/autodetect_mouse boolean true

# Monitor autodetection is recommended.
xserver-xorg xserver-xorg/autodetect_monitor boolean true
# Uncomment if you have an LCD display.
xserver-xorg xserver-xorg/config/monitor/lcd boolean true
# X has three configuration paths for the monitor. Here's how to preseed
# the "medium" path, which is always available. The "simple" path may not
# be available, and the "advanced" path asks too many questions.
xserver-xorg xserver-xorg/config/monitor/selection-method \
       select medium
xserver-xorg xserver-xorg/config/monitor/mode-list \
       select 1024x768 @ 60 Hz