py3: make test-ancestors.py pass on Python 3 with C extensions

# skip-blame just some b prefixes

tests/test-ancestor.py

@@ -220,9 +220,9 b' def test_lazyancestors():'
 # DAGs that have been known to be problematic, and, optionally, known pairs
 # of revisions and their expected ancestor list.
 dagtests = [
-    ('+2*2*2/*3/2', {}),
-    ('+3*3/*2*2/*4*4/*4/2*4/2*2', {}),
-    ('+2*2*/2*4*/4*/3*2/4', {(6, 7): [3, 5]}),
+    (b'+2*2*2/*3/2', {}),
+    (b'+3*3/*2*2/*4*4/*4/2*4/2*2', {}),
+    (b'+2*2*/2*4*/4*/3*2/4', {(6, 7): [3, 5]}),
 ]
 def test_gca():
     u = uimod.ui.load()