commit https://github.com/vim/vim/commit/95f096030ed1a8afea028f2ea295d6f6a70f466f Author: Bram Moolenaar <Bram@vim.org> Date: Thu Nov 10 20:01:45 2016 +0100 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.

--- a/src/window.c
+++ b/src/window.c
@@ -2538,7 +2538,7 @@ win_close_othertab(win_T *win, int free_
 		;
 	    if (ptp == NULL)
 	    {
-		EMSG2(_(e_intern2), "win_close_othertab()");
+		internal_error("win_close_othertab()");
 		return;
 	    }
 	    ptp->tp_next = tp->tp_next;