[pkg] Use io.open with utf-8 encoding to read long description from README This forces decoding so that this is consistent between Python 2 and 3 as, in Python 3, decoding which would occur anyways and may fail depending on the environment locale settings.

etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances