[product/ERP5Type] Introduce Log.py for compatibility

Without it, it is not possible to upgrade instances since:
48c45fbd

[test/upgradeOldDataFS] use UI callables
Ensure the admin will able to trigger the upgrader
5 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

01:34:07

failed ERP5.UnitTest-Master

09:39:59

failed ERP5.UnitTest-Master.Medusa

02:03:31

passed SlapOS.Eggs.UnitTest-Master.Python2

00:34:04

passed SlapOS.Eggs.UnitTest-Master.Python3

00:23:11