I made two changes to the PNG image file:

$ hg log pep-0495-fold.png
changeset:   6056:e6c82824b10f
user:        Alexander Belopolsky <alexander.belopolsky@gmail.com>
date:        Sun Sep 20 20:25:12 2015 -0400
summary:     PEP 495: Added a gap sketch.
changeset:   6024:8c8352ff4668
user:        Alexander Belopolsky <alexander.belopolsky@gmail.com>
date:        Sun Aug 30 22:49:58 2015 -0400
summary:     PEP 495: Added a vertical segment to the graph.
changeset:   6022:db95b4037a82
user:        Alexander Belopolsky <alexander.belopolsky@gmail.com>
date:        Sun Aug 30 22:27:51 2015 -0400
summary:     PEP 495: Added png rasterization of the fold sketch.

but the PEP page still shows the old image.