Force requirement update to avoir "six" version conflict.
Force requirement update to avoir "six" version conflict.

`Pre-commit` and `virtualenv` both require the 'six' package already
installed by default at version 1.11 on ubunto

This version isn't enough for `virtualenv` which requires `six >= 1.12`

Tisseo/navitia,Tisseo/navitia,CanalTP/navitia,CanalTP/navitia,Tisseo/navitia,xlqian/navitia,xlqian/navitia,CanalTP/navitia,CanalTP/navitia,xlqian/navitia,xlqian/navitia,xlqian/navitia,Tisseo/navitia,Tisseo/navitia,CanalTP/navitia