Don't create your own engine; bind migrate_engine to your metadata

    """

    #==========================================================================

    # Change unique constraints of table `repo_to_perm`

    #==========================================================================

    from kallithea.lib.dbmigrate.schema.db_1_3_0 import UserRepoToPerm

    tbl = UserRepoToPerm().__table__

    new_cons = UniqueConstraint('user_id', 'repository_id', 'permission_id', table=tbl)

    new_cons.create()

    old_cons = None

    if migrate_engine.name in ['mysql']:

        old_cons = UniqueConstraint('user_id', 'repository_id', table=tbl, name="user_id")

    elif migrate_engine.name in ['postgresql']:

        old_cons = UniqueConstraint('user_id', 'repository_id', table=tbl)

    else:

        # sqlite doesn't support dropping constraints...

        print """Please manually drop UniqueConstraint('user_id', 'repository_id')"""

    if old_cons:

        try:

            old_cons.drop()

        except Exception as e:

            # we don't care if this fails really... better to pass migration than

            print 'Failed to remove Unique for user_id, repository_id reason %s' % e

    #==========================================================================

    # fix uniques of table `user_repo_group_to_perm`

    #==========================================================================

    from kallithea.lib.dbmigrate.schema.db_1_3_0 import UserRepoGroupToPerm

    tbl = UserRepoGroupToPerm().__table__

    new_cons = UniqueConstraint('group_id', 'permission_id', 'user_id', table=tbl)

    new_cons.create()

    old_cons = None

    # fix uniqueConstraints

    if migrate_engine.name in ['mysql']:

        #mysql is giving troubles here...

        old_cons = UniqueConstraint('group_id', 'permission_id', table=tbl, name="group_id")

    elif migrate_engine.name in ['postgresql']:

        old_cons = UniqueConstraint('group_id', 'permission_id', table=tbl, name='group_to_perm_group_id_permission_id_key')

    else:

        # sqlite doesn't support dropping constraints...

        print """Please manually drop UniqueConstraint('group_id', 'permission_id')"""

    if old_cons:

        try:

            old_cons.drop()

        except Exception as e:

            # we don't care if this fails really... better to pass migration than

            print 'Failed to remove Unique for user_id, repository_id reason %s' % e

    return

def downgrade(migrate_engine):

    meta = MetaData()

    meta.bind = migrate_engine