feat: retry google.auth TransportError and requests ConnectionError (googleapis#178)

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Fixes googleapis#176 🦕

Author: parthea

google/api_core/retry.py

@@ -62,11 +62,13 @@ def check_if_exists():
 import random
 import time
 
+import requests.exceptions
 import six
 
 from google.api_core import datetime_helpers
 from google.api_core import exceptions
 from google.api_core import general_helpers
+from google.auth import exceptions as auth_exceptions
 
 _LOGGER = logging.getLogger(__name__)
 _DEFAULT_INITIAL_DELAY = 1.0  # seconds
@@ -101,6 +103,8 @@ def if_exception_type_predicate(exception):
     exceptions.InternalServerError,
     exceptions.TooManyRequests,
     exceptions.ServiceUnavailable,
+    requests.exceptions.ConnectionError,
+    auth_exceptions.TransportError,
 )
 """A predicate that checks if an exception is a transient API error.
 

tests/unit/test_retry.py

@@ -18,9 +18,11 @@
 
 import mock
 import pytest
+import requests.exceptions
 
 from google.api_core import exceptions
 from google.api_core import retry
+from google.auth import exceptions as auth_exceptions
 
 
 def test_if_exception_type():
@@ -42,6 +44,8 @@ def test_if_transient_error():
     assert retry.if_transient_error(exceptions.InternalServerError(""))
     assert retry.if_transient_error(exceptions.TooManyRequests(""))
     assert retry.if_transient_error(exceptions.ServiceUnavailable(""))
+    assert retry.if_transient_error(requests.exceptions.ConnectionError(""))
+    assert retry.if_transient_error(auth_exceptions.TransportError(""))
     assert not retry.if_transient_error(exceptions.InvalidArgument(""))