Improve error about unsupported subscription target relations

When Who What
2019-01-13 08:07:48 Michael Paquier (michael-kun) Closed in commitfest 2019-01 with status: Committed
2019-01-13 08:07:48 Michael Paquier (michael-kun) Changed committer to michael-kun
2019-01-02 20:30:51 Peter Eisentraut (petere) New status: Waiting on Author
2018-12-29 15:21:02 Peter Eisentraut (petere) Added petere as reviewer
2018-12-06 02:35:30 Amit Langote (amitlan) Changed authors to Amit Langote (amitlan)
2018-12-06 02:35:24 Amit Langote (amitlan) Attached mail thread 41799bee-40eb-7bb5-80b1-325ce17518bc@lab.ntt.co.jp
2018-12-06 02:35:24 Amit Langote (amitlan) Created patch record