contrib/import-checker.py

--- a/contrib/import-checker.py	Mon Apr 09 20:49:39 2018 +0900
+++ b/contrib/import-checker.py	Mon Apr 09 20:51:23 2018 +0900
@@ -31,7 +31,6 @@
     # for cffi modules to re-export pure functions
     'mercurial.pure.base85',
     'mercurial.pure.bdiff',
-    'mercurial.pure.diffhelpers',
     'mercurial.pure.mpatch',
     'mercurial.pure.osutil',
     'mercurial.pure.parsers',