Port extractxml to Python 3 with minor typo fixes
Summary: Minor porting with some typos fixed, in case it will be needed some day
Test Plan: Tested with https://phabricator.kde.org/D25405 and seems to work as expected.
Reviewers: Localization, adrianchavesfernandez
Reviewed By: adrianchavesfernandez
Subscribers: kde-edu
Tags: KDE Edu
Differential Revision: https://phabricator.kde.org/D25532