There's a merged pull request on the void-packages repository

python-msgpack: update to 1.0.0
https://github.com/void-linux/void-packages/pull/19482

Description:
The Neovim plugin Deoplete complains if python-msgpack isn't version 1.0.0, I'm not 100% sure this is a release because github's treating it like it's just a tag.