explore other pgp libraries

python-gnupg is being bringing a lot of headaches, the code is unmantained (or maintaned by us) and has a lot of things I'm struggling to understand (or just garbage??). We should consider other options.

Should we use python-gpg? Which is a grapper to gpgme maintained by gnupg upstream. This brings support for everything on gnupg, so probably everything that we need. Bug gnupg is sometimes a bit of a pain to put it in bundles as has many daemons and is being designed for a different use case than ours, it ends up feeling hacky sometimes.

Should we use PGPy? A pure python implementation of OpenPGP. It will be smaller and easier to bundle. But it might miss stuff that we use, or bring more security issues as gnupg has many eyes.

I will give a try to port keymanager to both of them and see what comes out of it.