1.2 is totally broken with Python 3 (cannot write binary data to the port, only encoded Unicode which is nonsense). Please bump to 1.3.
commit 4b24d0760bd526b237a8a2ba2cee50cfc2deb487 Author: Jeroen Roovers <jer@gentoo.org> Date: Fri Jul 20 05:57:23 2018 +0200 dev-embedded/libftdi: Version 1.4. Package-Manager: Portage-2.3.43, Repoman-2.3.10