--- a/mercurial/crecord.py	Sat May 19 18:45:53 2018 +0530
+++ b/mercurial/crecord.py	Sat May 19 18:47:20 2018 +0530
@@ -554,7 +554,7 @@
     """
     chunkselector = curseschunkselector(headerlist, ui, operation)
     if testfn and os.path.exists(testfn):
-        testf = open(testfn)
+        testf = open(testfn, 'rb')
         testcommands = [x.rstrip('\n') for x in testf.readlines()]
         testf.close()
         while True: