fix py2 MagicMock(sys.stderr).encoding in tests

tests/func/test_checkout.py

@@ -407,11 +407,15 @@ class TestCheckoutShouldHaveSelfClearingProgressBar(TestDvc):
         self._prepare_repo()
 
     def test(self):
+        encoding = sys.stderr.encoding
         with self._caplog.at_level(logging.INFO, logger="dvc"), patch.object(
             sys, "stderr"
         ) as stdout_mock:
             self.stdout_mock = logger.handlers[0].stream = stdout_mock
 
+            if sys.version_info[:1] < (3,):
+                sys.stderr.encoding = encoding
+
             ret = main(["checkout"])
             self.assertEqual(0, ret)