cubicweb #1251298 add_cube in migration script doesn't allow to modify fsschema after [open]

In a migration script (cubicweb-conference 0.10.0), I have to modify the fsschema ( because of conflict between unique and required constraints). I add cubes in the same migration script. When I add my cubes after the fsschema modification, all works fine. But when I add the cubes before the modification of fsschema, the migration script failed (because of the conflict between unique and required constraints). So I suppose that the fsschema modification is not taking into account.

I attach the database dump which allow to replay the migration script 0.10.0 of cubicweb-conference.

priorityminor
typebug
done in<not specified>
load0.200
load left0.200
closed by<not specified>