Fix best_response_test to use standard python unittest.

PiperOrigin-RevId: 268561653
Change-Id: Iea114c27c415daa8f780b91f8d8ddf19ab6645dd

open_spiel/python/algorithms/best_response_test.py

@@ -19,13 +19,14 @@
 from __future__ import division
 from __future__ import print_function
 
-from google3.testing.pybase import googletest
+import unittest
+
 from open_spiel.python import policy
 from open_spiel.python.algorithms import best_response as pyspiel_best_response
 import pyspiel
 
 
-class BestResponseTest(googletest.TestCase):
+class BestResponseTest(unittest.TestCase):
 
   def test_best_response_is_a_policy(self):
     game = pyspiel.load_game("kuhn_poker")
@@ -50,4 +51,4 @@ def test_best_response_is_a_policy(self):
 
 
 if __name__ == "__main__":
-  googletest.main()
+  unittest.main()