UTF-8 encoding problem with $DBI::errstr

There seems to be something wrong with the UTF-8 encoding of
$DBI::errstr. The little program below, which tries to
connect to a non-existing PostgreSQL database, prints
in case of LC_ALL="en_US.utf8":

   could not translate host name "unknown" to address: [...]

which is fine, but for LC_ALL="de_DE.utf8", it prints

   konnte Hostname »unknown« nicht in Adresse übersetzen: [...]

which is wrong! It should be:

   konnte Hostname »unknown« nicht in Adresse übersetzen: [...]

Environment:

  OS         : Gentoo Linux x86_64
  PostgreSQL : 8.4
  Perl       : 5.8.8 and 5.10.1
  DBD::Pg    : 2.15.1, 2.16.0
  DBI        : 1.609
  LC_ALL     : de_DE.utf8

How to repeat:

---------------------------------------------------------------------

pgtest.pl (encoding is utf8)

use 5.8.0;
use utf8;
use strict;
use warnings;

use DBI;

binmode(STDOUT, ":utf8");
binmode(STDIN,  ":utf8");
binmode(STDERR, ":utf8");

print "\näöüÄÖÜß\n";

my %dbattr = (
    PrintError     => 0,
    RaiseError     => 0,
    AutoCommit     => 0,
    pg_enable_utf8 => 1
);

my $dbh = DBI->connect("DBI:Pg:dbname=10.0.30.2;host=unknown;port=10000",
                       'unknown', 'unknown', \%dbattr);

print $DBI::errstr . "\n";

---------------------------------------------------------------------

export LC_ALL="en_US.utf8"
perl pgtest.pl

   äöüÄÖÜß
   could not translate host name "unknown" to address: Name or service not known

(OK)

export LC_ALL="de_DE.iso8859-1"
perl pgtest.pl

   äöüÄÖÜß
   konnte Hostname »unknown« nicht in Adresse übersetzen: [...]

(OK)

export LC_ALL="de_DE.utf8"
perl pgtest.pl

   äöüÄÖÜß
   konnte Hostname »unknown« nicht in Adresse übersetzen: [...]

(not OK)