tests: compare against a bytes in test-lock.py

skip-blame: just b'' prefixes

Differential Revision: https://phab.mercurial-scm.org/D5771

contrib/python3-whitelist

@@ -363,6 +363,7 b' test-linelog.py'
 test-linerange.py
 test-locate.t
 test-lock-badness.t
+test-lock.py
 test-log-exthook.t
 test-log-linerange.t
 test-log.t

tests/test-lock.py

@@ -290,7 +290,7 b' class testlock(unittest.TestCase):'
             self.fail("unexpected lock acquisition")
         except error.LockHeld as why:
             self.assertTrue(why.errno == errno.ETIMEDOUT)
-            self.assertTrue(why.locker == "")
+            self.assertTrue(why.locker == b"")
             state.assertlockexists(False)
 
 if __name__ == '__main__':