diff -r 30ae924a9e00 -r b521b3a79afd contrib/check-code.py
--- a/contrib/check-code.py	Thu Oct 05 20:46:49 2017 +0000
+++ b/contrib/check-code.py	Thu Oct 05 14:18:55 2017 -0700
@@ -345,6 +345,7 @@
     (r'def.*[( ]\w+=\{\}', "don't use mutable default arguments"),
     (r'\butil\.Abort\b', "directly use error.Abort"),
     (r'^@(\w*\.)?cachefunc', "module-level @cachefunc is risky, please avoid"),
+    (r'^import atexit', "don't use atexit, use ui.atexit"),
     (r'^import Queue', "don't use Queue, use util.queue + util.empty"),
     (r'^import cStringIO', "don't use cStringIO.StringIO, use util.stringio"),
     (r'^import urllib', "don't use urllib, use util.urlreq/util.urlerr"),