patch 8.0.0422: Python test fails with Python 3.6

Problem:    Python test fails with Python 3.6.
Solution:   Convert new exception messages to old ones. (closes #1359)
diff --git a/src/version.c b/src/version.c
index c55ba19..3804bbe 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    422,
+/**/
     421,
 /**/
     420,