Got this to work on windows 7 GIMP 2.8.6 64bit..

The problem for me was with the getFilename function on line 19.

Add this import to the top of the file:

import ntpath

and change the function to the following

def getFilename(filename, suffix):
    head, tail = ntpath.split(filename)
    tail = tail.replace(".", suffix + ".")
    filename = head + "/" + tail
    return filename

Then it works like a charm.. thanks for the script.