There is a new pull request by mobinmob against master on the void-packages repository

https://github.com/mobinmob/void-packages python-tornado
https://github.com/void-linux/void-packages/pull/14925

python-tornado: update to 5.1.1.
5.1.1 is the last version that supports python2.x and python3.x both.

A patch file from https://github.com/void-linux/void-packages/pull/14925.patch is attached