BUG #14739: Wrong message when unique contraint fail

The following bug has been logged on the website:

Bug reference: 14739
Logged by: Fred BARROUD
Email address: fbd(at)datasapiens(dot)com
PostgreSQL version: 9.6.1
Operating system: Windows 10
Description:

I there,

I am testing PG on this query :

CREATE TABLE T_UNIK (ID INT UNIQUE);

INSERT INTO T_UNIK VALUES (1), (2), (3), (4), (5);

UPDATE T_UNIK SET ID = ID + 1;

I know that PG is unable to do this set based operation properly because it
does it row by row (which is a nonsense since it works on many RDBMS)

But the error message is strongly stupid :
ERROR: invalid byte sequence for encoding "UTF8": 0xe9 0x71 0x75

I am doing this through PG Admin 4 (v 1.1)

Thanks in advance