Port lc.py to Python 3

config/chroot_local-includes/usr/local/bin/lc.py should be migrated to python3

To test your changes: start a Tails nightly build from the feature/jessie branch (http://nightly.tails.boum.org/build_Tails_ISO_feature-jessie/), select “More options”, set an admin (sudo) password, apply your changes, and then:

/usr/local/bin/lc.py -g 1 --min 4 --max 10 /usr/share/amnesia/firstnames.txt

It should output a “random” nickname.

Parent Task: #5958

Original created by @alant on 10088 (Redmine)