/etc/X11# nvidia-settings -V
sh: pkg-config: not found
Writing X config file '/etc/X11/xorg.conf'
Traceback (most recent call last):
  File "/usr/share/screen-resolution-extra/nvidia-polkit.py", line 20, in <module>
    import gtk, gobject, sys, dbus, logging, os, re
ImportError: No module named gtk

ERROR: Unable to open X config file '/etc/X11/xorg.conf' for writing.