Add plpython code.

src/pl/plpython/plpython_error.sql

@@ -0,0 +1,9 @@
+
+-- 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');