cubicweb-dataio #3243599 multiple consecutive import [validation pending]

Multiple consecutive import seems to raise an error on required/unique attribute:

line 518, in _drop_table_constraints_indexes
self.session.system_sql(sql)
ProgrammingError: constraint "cw_location_cw_id_key" of relation "cw_location" does not exist
prioritynormal
typebug
done in0.3.1
load0.500
load left0.000
closed by<not specified>