test: Switch to unittest.mock (googleapis#1864)

As of Python 3.4, the unittest module in the standard library has
included mock, which means we can remove one external dependency.

Co-authored-by: Anthonios Partheniou <[email protected]>

noxfile.py

@@ -42,7 +42,6 @@
     "pytest-cov",
     "webtest",
     "coverage",
-    "mock",
 ]
 
 

tests/test__auth.py

@@ -13,11 +13,11 @@
 # limitations under the License.
 
 import unittest
+from unittest import mock
 
 import google.auth.credentials
 import google_auth_httplib2
 import httplib2
-import mock
 import oauth2client.client
 
 from googleapiclient import _auth

tests/test__helpers.py

@@ -15,10 +15,9 @@
 """Unit tests for googleapiclient._helpers."""
 
 import unittest
+from unittest import mock
 import urllib
 
-import mock
-
 from googleapiclient import _helpers
 
 

tests/test_discovery.py

@@ -35,14 +35,14 @@
 import re
 import sys
 import unittest
+from unittest import mock
 import urllib
 
 import google.api_core.exceptions
 import google.auth.credentials
 from google.auth.exceptions import MutualTLSChannelError
 import google_auth_httplib2
 import httplib2
-import mock
 from oauth2client import GOOGLE_TOKEN_URI
 from oauth2client.client import GoogleCredentials, OAuth2Credentials
 from parameterized import parameterized

tests/test_discovery_cache.py

@@ -19,8 +19,7 @@
 
 import datetime
 import unittest
-
-import mock
+from unittest import mock
 
 from googleapiclient.discovery_cache import DISCOVERY_DOC_MAX_AGE
 

tests/test_http.py

@@ -34,10 +34,10 @@
 import ssl
 import time
 import unittest
+from unittest import mock
 import urllib
 
 import httplib2
-import mock
 from oauth2client.client import Credentials
 
 from googleapiclient.discovery import build