DO $$ plpy.notice("This is plpythonu.") $$ LANGUAGE plpythonu;
NOTICE:  This is plpythonu.
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
CONTEXT:  Traceback (most recent call last):
  PL/Python anonymous code block, line 1, in <module>
    nonsense 
PL/Python anonymous code block