odd alter_generic regression failures

We seem to have an intermittent failure on the alter_generic tests that 
look like this:
      SET SESSION AUTHORIZATION regtest_alter_user1;      CREATE FUNCTION alt_func1(int) RETURNS int LANGUAGE sql
AS 'SELECT $1 + 1';   + ERROR:  permission denied for language sql      CREATE FUNCTION alt_func2(int) RETURNS int
LANGUAGEsql        AS 'SELECT $1 - 1';   + ERROR:  permission denied for language sql      CREATE AGGREGATE alt_agg1 (
     sfunc1 = int4pl, basetype = int4, stype1 = int4, initcond = 0      );
 

This has been seen on at least two buildfarm members: chough (Windows/MSVC) and smilodon (NetBSD/gcc). The fact that
it'sintermittent is rather worrying and puzzling.
 

cheers

andrew