PL/Python: Make tests pass with Python 3.5

The error message wording for AttributeError has changed in Python 3.5.
For the plpython_error test, add a new expected file.  In the
plpython_subtransaction test, we didn't really care what the exception
is, only that it is something coming from Python.  So use a generic
exception instead, which has a message that doesn't vary across
versions.

src/pl/plpython/expected/README

 Guide to alternative expected files:
 
 plpython_error_0.out			Python 2.4 and older
+plpython_error_5.out			Python 3.5 and newer
 
 plpython_unicode.out			server encoding != SQL_ASCII
 plpython_unicode_3.out			server encoding == SQL_ASCII

src/pl/plpython/expected/plpython_subtransaction.out

@@ -19,7 +19,7 @@ try:
         if what_error == "SPI":
             plpy.execute("INSERT INTO subtransaction_tbl VALUES ('oops')")
         elif what_error == "Python":
-            plpy.attribute_error
+            raise Exception("Python exception")
     except:
         exc = False
         subxact.__exit__(*sys.exc_info())
@@ -58,10 +58,10 @@ SELECT * FROM subtransaction_tbl;
 
 TRUNCATE subtransaction_tbl;
 SELECT subtransaction_test('Python');
-ERROR:  AttributeError: 'module' object has no attribute 'attribute_error'
+ERROR:  Exception: Python exception
 CONTEXT:  Traceback (most recent call last):
   PL/Python function "subtransaction_test", line 13, in <module>
-    plpy.attribute_error
+    raise Exception("Python exception")
 PL/Python function "subtransaction_test"
 SELECT * FROM subtransaction_tbl;
  i 
@@ -78,7 +78,7 @@ with plpy.subtransaction():
     if what_error == "SPI":
         plpy.execute("INSERT INTO subtransaction_tbl VALUES ('oops')")
     elif what_error == "Python":
-        plpy.attribute_error
+        raise Exception("Python exception")
 $$ LANGUAGE plpythonu;
 SELECT subtransaction_ctx_test();
  subtransaction_ctx_test 
@@ -110,10 +110,10 @@ SELECT * FROM subtransaction_tbl;
 
 TRUNCATE subtransaction_tbl;
 SELECT subtransaction_ctx_test('Python');
-ERROR:  AttributeError: 'module' object has no attribute 'attribute_error'
+ERROR:  Exception: Python exception
 CONTEXT:  Traceback (most recent call last):
   PL/Python function "subtransaction_ctx_test", line 8, in <module>
-    plpy.attribute_error
+    raise Exception("Python exception")
 PL/Python function "subtransaction_ctx_test"
 SELECT * FROM subtransaction_tbl;
  i 

src/pl/plpython/expected/plpython_subtransaction_0.out

@@ -19,7 +19,7 @@ try:
         if what_error == "SPI":
             plpy.execute("INSERT INTO subtransaction_tbl VALUES ('oops')")
         elif what_error == "Python":
-            plpy.attribute_error
+            raise Exception("Python exception")
     except:
         exc = False
         subxact.__exit__(*sys.exc_info())
@@ -58,10 +58,10 @@ SELECT * FROM subtransaction_tbl;
 
 TRUNCATE subtransaction_tbl;
 SELECT subtransaction_test('Python');
-ERROR:  AttributeError: 'module' object has no attribute 'attribute_error'
+ERROR:  Exception: Python exception
 CONTEXT:  Traceback (most recent call last):
   PL/Python function "subtransaction_test", line 13, in <module>
-    plpy.attribute_error
+    raise Exception("Python exception")
 PL/Python function "subtransaction_test"
 SELECT * FROM subtransaction_tbl;
  i 
@@ -78,7 +78,7 @@ with plpy.subtransaction():
     if what_error == "SPI":
         plpy.execute("INSERT INTO subtransaction_tbl VALUES ('oops')")
     elif what_error == "Python":
-        plpy.attribute_error
+        raise Exception("Python exception")
 $$ LANGUAGE plpythonu;
 ERROR:  could not compile PL/Python function "subtransaction_ctx_test"
 DETAIL:  SyntaxError: invalid syntax (line 3)

src/pl/plpython/expected/plpython_subtransaction_5.out

@@ -19,7 +19,7 @@ try:
         if what_error == "SPI":
             plpy.execute("INSERT INTO subtransaction_tbl VALUES ('oops')")
         elif what_error == "Python":
-            plpy.attribute_error
+            raise Exception("Python exception")
     except:
         exc = False
         subxact.__exit__(*sys.exc_info())
@@ -58,10 +58,10 @@ SELECT * FROM subtransaction_tbl;
 
 TRUNCATE subtransaction_tbl;
 SELECT subtransaction_test('Python');
-ERROR:  AttributeError: 'module' object has no attribute 'attribute_error'
+ERROR:  Exception: Python exception
 CONTEXT:  Traceback (most recent call last):
   PL/Python function "subtransaction_test", line 13, in <module>
-    plpy.attribute_error
+    raise Exception("Python exception")
 PL/Python function "subtransaction_test"
 SELECT * FROM subtransaction_tbl;
  i 
@@ -78,7 +78,7 @@ with plpy.subtransaction():
     if what_error == "SPI":
         plpy.execute("INSERT INTO subtransaction_tbl VALUES ('oops')")
     elif what_error == "Python":
-        plpy.attribute_error
+        raise Exception("Python exception")
 $$ LANGUAGE plpythonu;
 ERROR:  could not compile PL/Python function "subtransaction_ctx_test"
 DETAIL:  SyntaxError: invalid syntax (<string>, line 3)

src/pl/plpython/sql/plpython_subtransaction.sql

@@ -23,7 +23,7 @@ try:
         if what_error == "SPI":
             plpy.execute("INSERT INTO subtransaction_tbl VALUES ('oops')")
         elif what_error == "Python":
-            plpy.attribute_error
+            raise Exception("Python exception")
     except:
         exc = False
         subxact.__exit__(*sys.exc_info())
@@ -53,7 +53,7 @@ with plpy.subtransaction():
     if what_error == "SPI":
         plpy.execute("INSERT INTO subtransaction_tbl VALUES ('oops')")
     elif what_error == "Python":
-        plpy.attribute_error
+        raise Exception("Python exception")
 $$ LANGUAGE plpythonu;
 
 SELECT subtransaction_ctx_test();