There is an updated pull request by pfpulux against master on the void-packages repository

https://github.com/pfpulux/void-packages python-Flask-User
https://github.com/void-linux/void-packages/pull/18616

New package: python-Flask-User-0.6.21


A patch file from https://github.com/void-linux/void-packages/pull/18616.patch is attached