Update plpython_subtransaction alternative expected files

The original patch only targeted Python 2.6 and newer, since that is
what we have supported in PostgreSQL 13 and newer.  For older
branches, we need to fix it up for older Python versions.

src/pl/plpython/expected/plpython_subtransaction.out

@@ -239,7 +239,7 @@ AS $$
 try:
     with plpy.subtransaction() as s:
         s.__exit__(None, None, None)
-except ValueError as e:
+except ValueError, e:
     raise ValueError(e)
 $$ LANGUAGE plpythonu;
 SELECT subtransaction_exit_without_enter();

src/pl/plpython/expected/plpython_subtransaction_0.out

@@ -222,11 +222,14 @@ ERROR:  could not compile PL/Python function "subtransaction_enter_subtransactio
 DETAIL:  SyntaxError: invalid syntax (line 3)
 CREATE FUNCTION subtransaction_exit_subtransaction_in_with() RETURNS void
 AS $$
+try:
     with plpy.subtransaction() as s:
         s.__exit__(None, None, None)
+except ValueError, e:
+    raise ValueError(e)
 $$ LANGUAGE plpythonu;
 ERROR:  could not compile PL/Python function "subtransaction_exit_subtransaction_in_with"
-DETAIL:  SyntaxError: invalid syntax (line 3)
+DETAIL:  SyntaxError: invalid syntax (line 4)
 SELECT subtransaction_exit_without_enter();
 ERROR:  ValueError: this subtransaction has not been entered
 CONTEXT:  Traceback (most recent call last):

src/pl/plpython/expected/plpython_subtransaction_5.out

@@ -222,11 +222,14 @@ ERROR:  could not compile PL/Python function "subtransaction_enter_subtransactio
 DETAIL:  SyntaxError: invalid syntax (<string>, line 3)
 CREATE FUNCTION subtransaction_exit_subtransaction_in_with() RETURNS void
 AS $$
+try:
     with plpy.subtransaction() as s:
         s.__exit__(None, None, None)
+except ValueError, e:
+    raise ValueError(e)
 $$ LANGUAGE plpythonu;
 ERROR:  could not compile PL/Python function "subtransaction_exit_subtransaction_in_with"
-DETAIL:  SyntaxError: invalid syntax (<string>, line 3)
+DETAIL:  SyntaxError: invalid syntax (<string>, line 4)
 SELECT subtransaction_exit_without_enter();
 ERROR:  ValueError: this subtransaction has not been entered
 CONTEXT:  Traceback (most recent call last):

src/pl/plpython/sql/plpython_subtransaction.sql

@@ -161,7 +161,7 @@ AS $$
 try:
     with plpy.subtransaction() as s:
         s.__exit__(None, None, None)
-except ValueError as e:
+except ValueError, e:
     raise ValueError(e)
 $$ LANGUAGE plpythonu;