Description of problem:
Having a cluster not attached to any data center is not common, or recommended or helpful in any way, but it's possible and I saw it happen in one env here in QE.
If that happens that in the cluster column in DB storage_pool_id will be None for this cluster and that will cause this upgrade db_script to fail the engine upgrade - 04_01_0010_add_mac_pool_id_to_vds_group.sql:

SELECT fn_db_add_column('cluster',
                        'mac_pool_id',
                        'UUID REFERENCES mac_pools (id)');

UPDATE
  cluster AS c
SET
  mac_pool_id = (
      SELECT
        sp.mac_pool_id
      FROM
        storage_pool sp
      WHERE
        sp.id = c.storage_pool_id
    );

ALTER TABLE cluster ALTER COLUMN mac_pool_id SET NOT NULL;


solution is easy, just remove cluster and run engine-setup again.


Version-Release number of selected component (if applicable):
This was found when running engine-setup with one of the 4.1 upstream versions (not sure which, but master branch still has this same file so nothing changed), setup was done with db restored from a 4.0 env and that's why this was possible.

How reproducible:
always

Steps to Reproduce:
1. Create a data center in rhevm 4.0
2. Create a cluster in that data center.
3. Remove the data center leaving only the cluster.
4. Backup engine with engine-backup tool.
5. Install 4.1 rpms and all needed to install rhevm 4.1.
6. Restore engine database using engine-backup tool.
7. Run engine-setup.

Actual results:
Setup fails with the reason being '04_01_0010_add_mac_pool_id_to_vds_group.sql' got Null for storage_pool_id (I did not keep the log from that run, no need to re produce it's quite obvious).

Expected results:
engine-setup is successful.

Additional info: