Good morning!
I haven’t experienced this particular error, but it looks like PIL doesn’t recognise the Transparency in the image.
Maybe converting it something like below could help.
import Image
im = Image.open("image1.png")
im.show()
print im.mode
im.convert("RGBA").save("image2.png")
Also check this post python - PIL does not save transparency - Stack Overflow
Hope this helps
Cheers mrfabulous1 