Adrien Di Mascio <Adrien.DiMascio@logilab.fr> [Thu, 13 Oct 2016 15:31:02 +0200] rev 11792
[massive store] remove on_commit / on_rollback parameters
No actual use of this was found in client code.
If one wants to control this behaviour, he can always override
the commit method and add a try / except around
flush_entities in its own store