GifToRenPy is a Python 2 script that takes a .gif file and splits it into individual .png frames, so that an animation can be created from them in Ren'Py. The script also optionally creates a .rpy file with an image statement, defining the animation for you straight away.
The script should work in Python 3 just fine, but easygui and Pillow modules would need to be re-installed, as versions included are for Python 2 only.