diff --git a/tests/oauth2/test__client.py b/tests/oauth2/test__client.py
index 690a87b..54686df 100644
--- a/tests/oauth2/test__client.py
+++ b/tests/oauth2/test__client.py
@@ -13,13 +13,14 @@
 # limitations under the License.
 
 import datetime
-import http.client
 import json
 import os
-import urllib
 
 import mock
 import pytest
+import six
+from six.moves import http_client
+from six.moves import urllib
 
 from google.auth import _helpers
 from google.auth import crypt
@@ -74,7 +75,7 @@
     assert _client._parse_expiry({}) is None
 
 
-def make_request(response_data, status=http.client.OK):
+def make_request(response_data, status=http_client.OK):
     response = mock.create_autospec(transport.Response, instance=True)
     response.status = status
     response.data = json.dumps(response_data).encode("utf-8")
@@ -129,7 +130,7 @@
 
 
 def test__token_endpoint_request_error():
-    request = make_request({}, status=http.client.BAD_REQUEST)
+    request = make_request({}, status=http_client.BAD_REQUEST)
 
     with pytest.raises(exceptions.RefreshError):
         _client._token_endpoint_request(request, "http://example.com", {})
@@ -137,7 +138,7 @@
 
 def test__token_endpoint_request_internal_failure_error():
     request = make_request(
-        {"error_description": "internal_failure"}, status=http.client.BAD_REQUEST
+        {"error_description": "internal_failure"}, status=http_client.BAD_REQUEST
     )
 
     with pytest.raises(exceptions.RefreshError):
@@ -146,7 +147,7 @@
         )
 
     request = make_request(
-        {"error": "internal_failure"}, status=http.client.BAD_REQUEST
+        {"error": "internal_failure"}, status=http_client.BAD_REQUEST
     )
 
     with pytest.raises(exceptions.RefreshError):
@@ -159,7 +160,7 @@
     request_body = request.call_args[1]["body"].decode("utf-8")
     request_params = urllib.parse.parse_qs(request_body)
 
-    for key, value in params.items():
+    for key, value in six.iteritems(params):
         assert request_params[key][0] == value
 
 
diff --git a/tests/oauth2/test_sts.py b/tests/oauth2/test_sts.py
index b516c8a..e8e008d 100644
--- a/tests/oauth2/test_sts.py
+++ b/tests/oauth2/test_sts.py
@@ -12,12 +12,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import http.client
 import json
-import urllib
 
 import mock
 import pytest
+from six.moves import http_client
+from six.moves import urllib
 
 from google.auth import exceptions
 from google.auth import transport
@@ -67,7 +67,7 @@
         return sts.Client(cls.TOKEN_EXCHANGE_ENDPOINT, client_auth)
 
     @classmethod
-    def make_mock_request(cls, data, status=http.client.OK):
+    def make_mock_request(cls, data, status=http_client.OK):
         response = mock.create_autospec(transport.Response, instance=True)
         response.status = status
         response.data = json.dumps(data).encode("utf-8")
@@ -110,7 +110,7 @@
             "options": urllib.parse.quote(json.dumps(self.ADDON_OPTIONS)),
         }
         request = self.make_mock_request(
-            status=http.client.OK, data=self.SUCCESS_RESPONSE
+            status=http_client.OK, data=self.SUCCESS_RESPONSE
         )
 
         response = client.exchange_token(
@@ -145,7 +145,7 @@
             "subject_token_type": self.SUBJECT_TOKEN_TYPE,
         }
         request = self.make_mock_request(
-            status=http.client.OK, data=self.SUCCESS_RESPONSE
+            status=http_client.OK, data=self.SUCCESS_RESPONSE
         )
 
         response = client.exchange_token(
@@ -165,7 +165,7 @@
         """
         client = self.make_client()
         request = self.make_mock_request(
-            status=http.client.BAD_REQUEST, data=self.ERROR_RESPONSE
+            status=http_client.BAD_REQUEST, data=self.ERROR_RESPONSE
         )
 
         with pytest.raises(exceptions.OAuthError) as excinfo:
@@ -209,7 +209,7 @@
             "options": urllib.parse.quote(json.dumps(self.ADDON_OPTIONS)),
         }
         request = self.make_mock_request(
-            status=http.client.OK, data=self.SUCCESS_RESPONSE
+            status=http_client.OK, data=self.SUCCESS_RESPONSE
         )
 
         response = client.exchange_token(
@@ -247,7 +247,7 @@
             "subject_token_type": self.SUBJECT_TOKEN_TYPE,
         }
         request = self.make_mock_request(
-            status=http.client.OK, data=self.SUCCESS_RESPONSE
+            status=http_client.OK, data=self.SUCCESS_RESPONSE
         )
 
         response = client.exchange_token(
@@ -268,7 +268,7 @@
         """
         client = self.make_client(self.CLIENT_AUTH_BASIC)
         request = self.make_mock_request(
-            status=http.client.BAD_REQUEST, data=self.ERROR_RESPONSE
+            status=http_client.BAD_REQUEST, data=self.ERROR_RESPONSE
         )
 
         with pytest.raises(exceptions.OAuthError) as excinfo:
@@ -313,7 +313,7 @@
             "client_secret": CLIENT_SECRET,
         }
         request = self.make_mock_request(
-            status=http.client.OK, data=self.SUCCESS_RESPONSE
+            status=http_client.OK, data=self.SUCCESS_RESPONSE
         )
 
         response = client.exchange_token(
@@ -350,7 +350,7 @@
             "client_secret": CLIENT_SECRET,
         }
         request = self.make_mock_request(
-            status=http.client.OK, data=self.SUCCESS_RESPONSE
+            status=http_client.OK, data=self.SUCCESS_RESPONSE
         )
 
         response = client.exchange_token(
@@ -371,7 +371,7 @@
         """
         client = self.make_client(self.CLIENT_AUTH_REQUEST_BODY)
         request = self.make_mock_request(
-            status=http.client.BAD_REQUEST, data=self.ERROR_RESPONSE
+            status=http_client.BAD_REQUEST, data=self.ERROR_RESPONSE
         )
 
         with pytest.raises(exceptions.OAuthError) as excinfo: