Add Unicode support in PL/Python

PL/Python now accepts Unicode objects where it previously only accepted string
objects (for example, as return value).  Unicode objects are converted to the
PostgreSQL server encoding as necessary.

This change is also necessary for future Python 3 support, which treats all
strings as Unicode objects.

Since this removes the error conditions that the plpython_unicode test file
tested for, the alternative result files are no longer necessary.

src/pl/plpython/sql/plpython_trigger.sql

@@ -159,6 +159,22 @@ UPDATE trigger_test SET v = 'null' WHERE i = 0;
 DROP TRIGGER stupid_trigger3 ON trigger_test;
 
 
+-- Unicode variant
+
+CREATE FUNCTION stupid3u() RETURNS trigger
+AS $$
+    return u"foo"
+$$ LANGUAGE plpythonu;
+
+CREATE TRIGGER stupid_trigger3
+BEFORE UPDATE ON trigger_test
+FOR EACH ROW EXECUTE PROCEDURE stupid3u();
+
+UPDATE trigger_test SET v = 'null' WHERE i = 0;
+
+DROP TRIGGER stupid_trigger3 ON trigger_test;
+
+
 -- deleting the TD dictionary
 
 CREATE FUNCTION stupid4() RETURNS trigger
@@ -227,6 +243,23 @@ UPDATE trigger_test SET v = 'null' WHERE i = 0;
 DROP TRIGGER stupid_trigger7 ON trigger_test;
 
 
+-- Unicode variant
+
+CREATE FUNCTION stupid7u() RETURNS trigger
+AS $$
+    TD["new"] = {u'a': 'foo', u'b': 'bar'}
+    return "MODIFY"
+$$ LANGUAGE plpythonu;
+
+CREATE TRIGGER stupid_trigger7
+BEFORE UPDATE ON trigger_test
+FOR EACH ROW EXECUTE PROCEDURE stupid7u();
+
+UPDATE trigger_test SET v = 'null' WHERE i = 0;
+
+DROP TRIGGER stupid_trigger7 ON trigger_test;
+
+
 -- calling a trigger function directly
 
 SELECT stupid7();