BUG #5497: plpythonu gives cache lookup error

The following bug has been logged online:

Bug reference:      5497
Logged by:          David Gardner
Email address:      dgardner@creatureshop.com
PostgreSQL version: 9.0beta2
Operating system:   Debian Linux
Description:        plpythonu gives cache lookup error
Details:

hdpsdb=# CREATE OR REPLACE FUNCTION py_test(to_list text[])
  RETURNS text AS
$BODY$
return 'here'
$BODY$
  LANGUAGE 'plpythonu' VOLATILE;
CREATE FUNCTION
hdpsdb=# SELECT * FROM py_test('{"a","b","c"}');
ERROR:  cache lookup failed for type 98
CONTEXT:  PL/Python function "py_test"
hdpsdb=# SELECT version();
                                                 version

----------------------------------------------------------------------------
-----------------------------
 PostgreSQL 9.0beta2 on x86_64-pc-linux-gnu, compiled by GCC gcc-4.4.real
(Debian 4.4.4-3) 4.4.4, 64-bit
(1 row)

hdpsdb=#