patch 8.0.0074
Problem:    Cannot make Vim fail on an internal error.
Solution:   Add IEMSG() and IEMSG2(). (Domenique Pelle)  Avoid reporting an
            internal error without mentioning where.
diff --git a/src/gui_beval.c b/src/gui_beval.c
index 4a7c06e..8569f60 100644
--- a/src/gui_beval.c
+++ b/src/gui_beval.c
@@ -218,7 +218,7 @@
 
     if (mesg != NULL && mesgCB != NULL)
     {
-	EMSG(_("E232: Cannot create BalloonEval with both message and callback"));
+	IEMSG(_("E232: Cannot create BalloonEval with both message and callback"));
 	return NULL;
     }