def drop_unique_constraint(migrate_engine, table_name, uc_name, *columns,
                           **col_name_col_instance):
    if migrate_engine.name == "sqlite":
        _drop_unique_constraint_in_sqlite(migrate_engine, table_name, uc_name,
                                          **col_name_col_instance)
    else:
        meta = MetaData()
        meta.bind = migrate_engine
        t = Table(table_name, meta, autoload=True)
        uc = UniqueConstraint(*columns, table=t, name=uc_name)
        uc.drop()
This method drops UC from table and works for mysql, postgresql and
dataset/ETHPy150Open openstack/rack/rack/db/sqlalchemy/utils.py/drop_unique_constraint