Here is what I did. (You could probably do this yourself, but never mind :)

hg pull -r{default,2.7,3.5}
hg update default  # Update to the latest public revision
hg import --no-commit "$(xclip -o)"  # Apply your patch on top
hg diff -p > pep467.patch  # Make a new diff

If you look inside the patch file, the difference is that the Reitveld review system cannot handle “diff -r 3e41c0449b9c” from your file, but hopefully will know about “diff -r ebb23744a36c” in my version.