Using one of the animation extensions error

I am using an animation extension in inkscape and everytime I want to view my animation, I click playback, and then inkscape sends this message and I don't understand what they are talking about. Does anyone know what this means:

Inkscape has received additional data from the script executed. The script did not return an error, but this may indicate the results will not be as expected.

Traceback (most recent call last):
  File "animation_preview.py", line 38, in <module>
    from fltk import *
ImportError: No module named fltk