Convert the existing regression test scripts for the various optional

PLs to use the standard pg_regress infrastructure.  No changes in the
tests themselves.  Andrew Dunstan

src/pl/plpython/sql/plpython_error.sql

@@ -0,0 +1,13 @@
+
+-- test error handling, i forgot to restore Warn_restart in
+-- the trigger handler once. the errors and subsequent core dump were
+-- interesting.
+
+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');