Remove read_file/write_file tests. These were originally intended to

*fail*, to test that plpython didn't allow untrusted operations.
When we changed plpython to plpythonu because python didn't actually have
a secure sandbox mode, someone (probably me :-() misinterpreted the tests
as checking whether Python's file I/O works.  Which is a stupid thing for
us to be testing.  Remove it so we don't clutter the filesystem with
random temporary files.

src/pl/plpython/expected/plpython_error.out

@@ -19,16 +19,3 @@ SELECT valid_type('rick');
  
 (1 row)
 
--- Security sandbox tests
-SELECT write_file('/tmp/plpython','Only trusted users should be able to do this!');
-          write_file          
-------------------------------
- Wrote to file: /tmp/plpython
-(1 row)
-
-SELECT read_file('/tmp/plpython');
-                   read_file                   
------------------------------------------------
- Only trusted users should be able to do this!
-(1 row)
-

src/pl/plpython/expected/plpython_function.out

@@ -255,13 +255,6 @@ for r in rv:
 return seq
 '
 	LANGUAGE plpythonu;
-CREATE OR REPLACE FUNCTION read_file(text) RETURNS text AS '
-  return open(args[0]).read()
-' LANGUAGE plpythonu;
-CREATE OR REPLACE FUNCTION write_file(text,text) RETURNS text AS '
-  open(args[0],"w").write(args[1])
-  return "Wrote to file: %s" % args[0]
-' LANGUAGE plpythonu;
 --
 -- Universal Newline Support
 -- 

src/pl/plpython/sql/plpython_error.sql

@@ -7,7 +7,3 @@ SELECT invalid_type_uncaught('rick');
 SELECT invalid_type_caught('rick');
 SELECT invalid_type_reraised('rick');
 SELECT valid_type('rick');
-
--- Security sandbox tests
-SELECT write_file('/tmp/plpython','Only trusted users should be able to do this!');
-SELECT read_file('/tmp/plpython');

src/pl/plpython/sql/plpython_function.sql

@@ -298,15 +298,6 @@ return seq
 '
 	LANGUAGE plpythonu;
 
-CREATE OR REPLACE FUNCTION read_file(text) RETURNS text AS '
-  return open(args[0]).read()
-' LANGUAGE plpythonu;
-
-CREATE OR REPLACE FUNCTION write_file(text,text) RETURNS text AS '
-  open(args[0],"w").write(args[1])
-  return "Wrote to file: %s" % args[0]
-' LANGUAGE plpythonu;
-
 --
 -- Universal Newline Support
 --