The error message for undefined names *inside functions* (not for undefined
names on global level) has changed in Python 3.4 compared to 3.3.

Particularly error string "NameError: global name 'nonsense' is not defined"
has become "ERROR:  NameError: name 'nonsense' is not defined" in Python 3.4.

This patch also raises an exception, but the exceptin message is the same
across Python versions.

diff -up postgresql-9.3.4/src/pl/plpython/expected/plpython_do.out.python34 postgresql-9.3.4/src/pl/plpython/expected/plpython_do.out
--- postgresql-9.3.4/src/pl/plpython/expected/plpython_do.out.python34	2014-05-23 15:42:50.462783074 +0200
+++ postgresql-9.3.4/src/pl/plpython/expected/plpython_do.out	2014-05-23 16:09:28.501654085 +0200
@@ -4,9 +4,9 @@ CONTEXT:  PL/Python anonymous code block
 DO $$ plpy.notice("This is plpython2u.") $$ LANGUAGE plpython2u;
 NOTICE:  This is plpython2u.
 CONTEXT:  PL/Python anonymous code block
-DO $$ nonsense $$ LANGUAGE plpythonu;
-ERROR:  NameError: global name 'nonsense' is not defined
+DO $$ raise Exception("Sample error") $$ LANGUAGE plpythonu;
+ERROR:  Exception: Sample error
 CONTEXT:  Traceback (most recent call last):
   PL/Python anonymous code block, line 1, in <module>
-    nonsense 
+    raise Exception("Sample error") 
 PL/Python anonymous code block
diff -up postgresql-9.3.4/src/pl/plpython/sql/plpython_do.sql.python34 postgresql-9.3.4/src/pl/plpython/sql/plpython_do.sql
--- postgresql-9.3.4/src/pl/plpython/sql/plpython_do.sql.python34	2014-05-23 15:42:24.240756276 +0200
+++ postgresql-9.3.4/src/pl/plpython/sql/plpython_do.sql	2014-05-23 16:10:31.363475875 +0200
@@ -2,4 +2,4 @@ DO $$ plpy.notice("This is plpythonu.")
 
 DO $$ plpy.notice("This is plpython2u.") $$ LANGUAGE plpython2u;
 
-DO $$ nonsense $$ LANGUAGE plpythonu;
+DO $$ raise Exception("Sample error") $$ LANGUAGE plpythonu;