Skip test case stdlib ConnectionError on Python 2

Co-authored-by: Tres Seaver <tseaver@palladion.com>

Author: cojenco

tests/unit/test_retry.py

@@ -59,16 +59,13 @@ def test_w_requests_connection_error(self):
  exc = ValueError("testing")
  self.assertFalse(self._call_fut(exc))
 
+ @unittest.skipUnless(
+ "ConnectionError" in __builtins__.__dict__,
+ "No builtin 'ConnectionError' in Python 2",
+ )
  def test_w_stdlib_connection_error(self):
- from google.cloud.storage import retry
-
- try:
- exc = ConnectionError()
- self.assertTrue(self._call_fut(exc))
- self.assertTrue(ConnectionError in retry._RETRYABLE_TYPES)
- except NameError:
- pass
-
+ exc = ConnectionError()
+ self.assertTrue(self._call_fut(exc))
 
 class TestConditionalRetryPolicy(unittest.TestCase):
  def _make_one(self, retry_policy, conditional_predicate, required_kwargs):