BUG #6593: REASSIGN OWNED fails on extensions

The following bug has been logged on the website:

Bug reference: 6593
Logged by: Emiliano Leporati
Email address: emiliano(dot)leporati(at)gmail(dot)com
PostgreSQL version: 9.1.2
Operating system: FreeBSD 9.0
Description:

Steps to reproduce:

postgres=# create database failtest;
CREATE DATABASE
postgres=# \c failtest
You are now connected to database "failtest" as user "ubik".
failtest=# create extension citext;
CREATE EXTENSION
failtest=# create table foo(bar integer);
CREATE TABLE
failtest=# reassign owned by ubik to dev;
ERROR: unexpected classid 3079
failtest=# select relname from pg_class where oid = 3079;
relname
--------------
pg_extension
(1 row)

failtest=#