diff --git a/contrib/python3-whitelist b/contrib/python3-whitelist
--- a/contrib/python3-whitelist
+++ b/contrib/python3-whitelist
@@ -11,6 +11,7 @@ test-contrib-check-code.t
 test-contrib-check-commit.t
 test-ctxmanager.py
 test-diff-issue2761.t
+test-diff-newlines.t
 test-diff-reverse.t
 test-diff-subdir.t
 test-dirstate-nonnormalset.t
diff --git a/tests/test-diff-newlines.t b/tests/test-diff-newlines.t
--- a/tests/test-diff-newlines.t
+++ b/tests/test-diff-newlines.t
@@ -1,6 +1,6 @@
   $ hg init
 
-  $ $PYTHON -c 'file("a", "wb").write("confuse str.splitlines\nembedded\rnewline\n")'
+  $ $PYTHON -c 'open("a", "wb").write(b"confuse str.splitlines\nembedded\rnewline\n")'
   $ hg ci -Ama -d '1 0'
   adding a