line function doesn't work with 16 bit color

I've just been trying to learn Python using "How to Think Like a Computer Scientist". I reached this point where it refers to GASP and provides examples:

http://openbookproject.net//thinkCSpy/chap04.xhtml

Unfortunately Gasp wasn't included in the Ubuntu Python so went to FAQ 31 here, had a few false starts downloading and installing, but finally did.

Then tried the first example on that page above, and the circle drew and the box drew but the line errored out with:

>>> Line((100, 400), (580, 200))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.5/site-packages/gasp/api.py", line 87, in __init__
    backend.create_line(self)
  File "/usr/lib/python2.5/site-packages/gasp/backend.py", line 180, in create_line
    (end[0], flip_coords(end[1], obj.sprite.rect)), False)
ValueError: unsupported bit depth for aaline draw (supports 32 & 24 bit)

I don't know if this applies but I use a Thinkpad 600E and it has its graphics mode set to 16 bit color -- I have to do that to be able to run reasonably fast in Ubuntu. Other than GASP's line drawing function, I haven't had a single problem running anything else graphically in Ubuntu -- including vector graphics draw programs, 3D CAD renderers, and videos.

In fact the GASP box and circle functions drew fine -- only the line function had this problem.

Computer:Thinkpad 600E, Ubuntu 7.10, Python, 1024 x 768 x 16 bit color