logilab-database #69607 backup_commands() for sqlite deletes the db [validation pending]

logilab/database/sqlite.py: return [['gzip', dbname], ['mv', dbname + '.gz', backupfile]]

This results in dbname not existing afterwards, because gzip deletes it after compressing it. This kind of breaks cubicweb-ctl upgrade since the first step is to make a backup of the db.

done in1.6.2
load left0.000
closed by#37d856bfd6f3 Make sqlite backup and restore commands work (closes #69607)