\d+ fails on index on partition

For indices inherited from relkind=p:

pryzbyj=# CREATE TABLE tt(i int)PARTITION BY RANGE(i);
pryzbyj=# CREATE TABLE tt1 PARTITION OF tt DEFAULT;
pryzbyj=# CREATE INDEX ON tt((0+i));
pryzbyj=# ALTER INDEX tt1_expr_idx ALTER COLUMN 1 SET STATISTICS 123;
pryzbyj=# \d+ tt1_expr_idx 
ERROR:  42809: "tt1_expr_idx" is an index
LOCATION:  heap_open, heapam.c:1305

Failing due to:
********* QUERY **********
SELECT inhparent::pg_catalog.regclass,
  pg_catalog.pg_get_expr(c.relpartbound, inhrelid),
  pg_catalog.pg_get_partition_constraintdef(inhrelid)
FROM pg_catalog.pg_class c JOIN pg_catalog.pg_inherits i ON c.oid = inhrelid
WHERE c.oid = '40129092' AND c.relispartition;
**************************

pg_get_partition_constraintdef() doesn't like being passed a relkind='I',
"ATTACH"ed index, which I guess is included in pg_inherit (commit 8b08f7d48):

pryzbyj=# SELECT inhparent::regclass, inhrelid::regclass, * FROM pg_inherits WHERE inhrelid='tt1_expr_idx'::regclass;
inhparent | tt_expr_idx
inhrelid  | tt1_expr_idx
inhrelid  | 40129092
inhparent | 40129091
inhseqno  | 1

I'll spare you the burden of any fix I might attempt to cobble together.

Justin