WIP: Remove TransactionError.get_code() function

tests/test_tickets.py

@@ -87,7 +87,7 @@ def test_ticket_103a():
             rt.update(strict=True)
         exc = e.value
         print(exc)
-        assert 128 == int(exc.get_errors()[0].get_code())
+        assert 128 == int(exc.errors[0].code)
         rt = exc.entities[0]
         assert not rt.is_valid()