Fix AttributeError for "lang" on repo/client connections This is a regression introduced by b48020a80dc3, which removed call to set_language from the `req._set_user` method. This is fine, but we still want a language on connections, so we've to handle it if necesary in Connection.__enter__ (i.e. once connection is properly open). When using pyramid front-end, which has a users cache, we've to cache its language as well because we must not access its preferred_language method since it's not bound to a proper connection.

/var/log/cubicweb/*.log {
        weekly
        missingok
        rotate 10
        compress
        delaycompress
        notifempty
        create 640 root adm
        sharedscripts
        postrotate
           if [ -x /usr/sbin/invoke-rc.d ]; then \
              invoke-rc.d cubicweb reload > /dev/null 2>&1; \
           else \
              /etc/init.d/cubicweb reload > /dev/null 2>&1; \
           fi; \
        endscript
}