Remove some Python 2 compatibility code. (#6624)

python/ray/tune/tests/test_sync.py

@@ -8,6 +8,7 @@ import shutil
 import sys
 import tempfile
 import unittest
+from unittest.mock import patch
 
 import ray
 from ray.rllib import _register_all
@@ -16,11 +17,6 @@ from ray import tune
 from ray.tune import TuneError
 from ray.tune.syncer import CommandBasedClient
 
-if sys.version_info >= (3, 3):
-    from unittest.mock import patch
-else:
-    from mock import patch
-
 
 class TestSyncFunctionality(unittest.TestCase):
     def setUp(self):
@@ -214,5 +210,4 @@ class TestSyncFunctionality(unittest.TestCase):
 
 if __name__ == "__main__":
     import pytest
-    import sys
     sys.exit(pytest.main(["-v", __file__]))