Fix python3 build.

dulwich/tests/test_repository.py

@@ -884,7 +884,7 @@ class BuildRepoRootTests(TestCase):
         r = self._repo
         os.mkdir(os.path.join(r.path, 'c'))
         r.stage(['c'])
-        self.assertEqual(['a'], list(r.open_index()))
+        self.assertEqual([b'a'], list(r.open_index()))
 
     @skipIf(sys.platform == 'win32' and sys.version_info[:2] >= (3, 6),
             'tries to implicitly decode as utf8')