Fix python3 build

dulwich/tests/test_client.py

@@ -718,10 +718,10 @@ class LocalGitClientTests(TestCase):
         ret = c.fetch_pack(s.path, lambda heads: [], graph_walker=walker,
             pack_data=out.write)
         self.assertEqual({
-            'HEAD': 'a90fa2d900a17e99b433217e988c4eb4a2e9a097',
-            'refs/heads/master': 'a90fa2d900a17e99b433217e988c4eb4a2e9a097',
-            'refs/tags/mytag': '28237f4dc30d0d462658d6b937b08a0f0b6ef55a',
-            'refs/tags/mytag-packed': 'b0931cadc54336e78a1d980420e3268903b57a50'
+            b'HEAD': b'a90fa2d900a17e99b433217e988c4eb4a2e9a097',
+            b'refs/heads/master': b'a90fa2d900a17e99b433217e988c4eb4a2e9a097',
+            b'refs/tags/mytag': b'28237f4dc30d0d462658d6b937b08a0f0b6ef55a',
+            b'refs/tags/mytag-packed': b'b0931cadc54336e78a1d980420e3268903b57a50'
             }, ret)
         self.assertEqual(b"PACK\x00\x00\x00\x02\x00\x00\x00\x00\x02\x9d\x08"
             b"\x82;\xd8\xa8\xea\xb5\x10\xadj\xc7\\\x82<\xfd>\xd3\x1e", out.getvalue())