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/hashtab.c b/src/hashtab.c
index d8d3aed..658bfb9 100644
--- a/src/hashtab.c
+++ b/src/hashtab.c
@@ -210,7 +210,7 @@
     hi = hash_lookup(ht, key, hash);
     if (!HASHITEM_EMPTY(hi))
     {
-	EMSG2(_(e_intern2), "hash_add()");
+	internal_error("hash_add()");
 	return FAIL;
     }
     return hash_add_item(ht, hi, key, hash);