chore: remove use of old external "mock" module (#1786)

_mock is now part of the Python standard library, available as [unittest.mock](https://docs.python.org/dev/library/unittest.mock.html) in Python 3.3 onwards._

https://togithub.com/testing-cabal/mock

Author: a-detiste

setup.py

@@ -56,7 +56,6 @@
     "grpcio",
     "flask",
     "freezegun",
-    "mock",
     # TODO(https://github.com/googleapis/google-auth-library-python/issues/1736): Remove `oauth2client` from testing requirements once an extra is added for `oauth2client` dependency.
     "oauth2client",
     *pyjwt_extra_require,

system_tests/system_tests_sync/test_external_accounts.py

@@ -48,7 +48,7 @@
 from http.server import HTTPServer
 from google.oauth2 import service_account
 import pytest
-from mock import patch
+from unittest.mock import patch
 
 # Populate values from the output of scripts/setup_external_accounts.sh.
 _AUDIENCE_OIDC = "//iam.googleapis.com/projects/79992041559/locations/global/workloadIdentityPools/pool-73wslmxn/providers/oidc-73wslmxn"

system_tests/system_tests_sync/test_mtls_http.py

@@ -13,10 +13,10 @@
 # limitations under the License.
 
 import json
-import mock
 import os
 import time
 from os import path
+from unittest import mock
 
 
 import google.auth

tests/compute_engine/test__metadata.py

@@ -17,8 +17,8 @@
 import importlib
 import json
 import os
+from unittest import mock
 
-import mock
 import pytest  # type: ignore
 import requests
 

tests/compute_engine/test__mtls.py

@@ -16,8 +16,8 @@
 #
 
 from pathlib import Path
+from unittest import mock
 
-import mock
 import pytest  # type: ignore
 import requests
 

tests/compute_engine/test_credentials.py

@@ -14,8 +14,8 @@
 import base64
 import datetime
 import os
+from unittest import mock
 
-import mock
 import pytest  # type: ignore
 import responses  # type: ignore
 

tests/conftest.py

@@ -14,8 +14,8 @@
 
 import os
 import sys
+from unittest import mock
 
-import mock
 import pytest  # type: ignore
 
 

tests/crypt/test__python_rsa.py

@@ -15,8 +15,8 @@
 import io
 import json
 import os
+from unittest import mock
 
-import mock
 from pyasn1_modules import pem  # type: ignore
 import pytest  # type: ignore
 import rsa  # type: ignore

tests/oauth2/test__client.py

@@ -16,9 +16,9 @@
 import http.client as http_client
 import json
 import os
+from unittest import mock
 import urllib
 
-import mock
 import pytest  # type: ignore
 
 from google.auth import _helpers

tests/oauth2/test_challenges.py

@@ -17,8 +17,8 @@
 import base64
 import os
 import sys
+from unittest import mock
 
-import mock
 import pytest  # type: ignore
 import pyu2f  # type: ignore