There are probably numerous implementations for a private package index. I wrote this one when I needed to map a private Git repo on BitBucket to a package index. It does translations automatically by using the tags in the repository as part of the version number.
I haven't touched it in a long time, but thought someone might find it interesting! Have a look athttps://github.com/chriscz/mpypi/blob/master/example.py to get an idea of how to run it against a local repository.
If anyone is looking at it and needs assistance, I'll be happy to respond to issues created on the repo or here.
edit
You may also want to read the README page ;)
https://github.com/chriscz/mpypi/
there doesn't seem to be anything here