contrib/import-checker.py

--- a/contrib/import-checker.py	Thu Jul 12 12:11:20 2018 -0700
+++ b/contrib/import-checker.py	Thu Aug 16 02:08:13 2018 +0200
@@ -28,6 +28,8 @@
     'mercurial.hgweb.request',
     'mercurial.i18n',
     'mercurial.node',
+    # for revlog to re-export constant to extensions
+    'mercurial.revlogutils.constants',
     # for cffi modules to re-export pure functions
     'mercurial.pure.base85',
     'mercurial.pure.bdiff',