Quick hack to un-break plpython regression tests.

It's not clear to me what should happen to the other plpython_unicode
variant expected files, but this patch gets things passing on my own
machines and at least some of the buildfarm.

src/pl/plpython/expected/plpython_unicode_3.out

@@ -41,8 +41,7 @@ SELECT * FROM unicode_test;
 SELECT unicode_plan1();
 WARNING:  PL/Python: plpy.Error: unrecognized error in PLy_spi_execute_plan
 CONTEXT:  PL/Python function "unicode_plan1"
-ERROR:  PL/Python: could not convert Python Unicode object to PostgreSQL server encoding
-DETAIL:  UnicodeEncodeError: 'ascii' codec can't encode character u'\x80' in position 0: ordinal not in range(128)
+ERROR:  PL/Python: plpy.SPIError: PL/Python: could not convert Python Unicode object to PostgreSQL server encoding
 CONTEXT:  PL/Python function "unicode_plan1"
 SELECT unicode_plan2();
  unicode_plan2