Please describe the problem:
if a pygtk program is directly located in /usr/lib and there is a
/usr/lib/gtk-2.0 directory (part of gtk+-2.x) then the gtk.require() function
assumes that this is the location of pygtk modules and appends "/usr/lib/" to
sys.path.
The pygtk program can't run because gtk, gnome, ... can't be imported because
the /usr/lib and not the correct directory (where the pygtk modules can be
found) is used

Steps to reproduce:
1. just try this little program:
#!/usr/bin/env python
import sys
import pygtk;
pygtk.require("2.0")
import gnome
import gc
import gtk
2. make sure you have a /usr/lib/gtk-2.0 directory
3. copy the program to /usr/bin and /usr/lib
4. python /usr/bin/bugtest.py
5. python /usr/lib/bugtest.py


Actual results:
the program in /usr/lib prints an error because it can't find the pygtk modules:
Traceback (most recent call last):

+ Trace 63438

and the program in /usr/bin works fine

Expected results:
that the python search path is correct

Does this happen every time?
yes

Other information:
the attached patch adds a sanity check to pygtk.py which solves the problem