BUG #12209: Temporary functions may cause pg_dump to fail

The following bug has been logged on the website:

Bug reference:      12209
Logged by:          Morten Hustveit
Email address:      morten.hustveit@gmail.com
PostgreSQL version: 9.4beta2
Operating system:   Debian
Description:

Note: Reported version is 9.4rc1, which is not available in the dropdown
box.

My second daily pg_dump backup after upgrading from 9.1 to 9.4rc1 failed
with this output:

pg_dump: [archiver (db)] query failed: ERROR:  cache lookup failed for
function 106830342
pg_dump: [archiver (db)] query was: SELECT tableoid, oid, proname, prolang,
pronargs, proargtypes, prorettype, proacl, pronamespace,
pg_catalog.pg_get_function_identity_arguments(oid) AS proiargs,(SELECT
rolname FROM pg_catalog.pg_roles WHERE oid = proowner) AS rolname FROM
pg_proc p WHERE NOT proisagg AND (pronamespace != (SELECT oid FROM
pg_namespace WHERE nspname = 'pg_catalog')
  AND NOT EXISTS (SELECT 1 FROM pg_depend WHERE classid =
'pg_proc'::regclass AND objid = p.oid AND deptype = 'i'))

The query did not fail when I reran it in psql.

I did not modify any non-temporary functions that day, but I continuously
run programs that create function ins the pg_temp schema.