[test] Add a test ensuring new cube built from skeleton is flake8-compliant And make skeleton files actually flake8-compliant henceforth.

#! /bin/sh -e

if [ -x "/etc/init.d/cubicweb-ctl" ]; then
    invoke-rc.d cubicweb-ctl restart || true
fi
 
 
#DEBHELPER#
 
exit 0