--- a/mercurial/match.py	Sat Aug 17 15:43:41 2019 +0900
+++ b/mercurial/match.py	Sat Aug 17 10:25:04 2019 +0900
@@ -25,7 +25,7 @@
     stringutil,
 )
 
-rustmod = policy.importrust('filepatterns')
+rustmod = policy.importrust(r'filepatterns')
 
 allpatternkinds = ('re', 'glob', 'path', 'relglob', 'relpath', 'relre',
                    'rootglob',