--- a/tests/test-grep.t	Thu Mar 01 23:58:21 2018 +0530
+++ b/tests/test-grep.t	Thu Mar 01 23:59:20 2018 +0530
@@ -271,7 +271,7 @@
 
 match in last "line" without newline
 
-  $ $PYTHON -c 'fp = open("noeol", "wb"); fp.write("no infinite loop"); fp.close();'
+  $ $PYTHON -c 'fp = open("noeol", "wb"); fp.write(b"no infinite loop"); fp.close();'
   $ hg ci -Amnoeol
   adding noeol
   $ hg grep loop