diff -r 813e726e5343 -r eb2945f0a4a1 mercurial/ui.py
--- a/mercurial/ui.py	Wed Aug 01 10:23:57 2018 -0400
+++ b/mercurial/ui.py	Thu Jul 19 15:21:28 2018 -0400
@@ -392,7 +392,7 @@
     def readconfig(self, filename, root=None, trust=False,
                    sections=None, remap=None):
         try:
-            fp = open(filename, u'rb')
+            fp = open(filename, r'rb')
         except IOError:
             if not sections: # ignore unless we were looking for something
                 return