refactor: switch from mock to unittest.mock (#34844)

As of Python 3.3, the 3rd-party `mock` package has been subsumed into the
standard `unittest.mock` package. Refactoring tests to use the latter will
allow us to drop `mock` as a dependency, which is currently coming in
transitively through requirements/edx/paver.in.

We don't actually drop the `mock` dependency in this PR. That will happen
naturally in:

* https://github.com/openedx/edx-platform/pull/34830

scripts/user_retirement/tests/test_get_learners_to_retire.py

@@ -1,11 +1,11 @@
 """
 Test the get_learners_to_retire.py script
 """
+from unittest.mock import DEFAULT, patch
 
 import os
 
 from click.testing import CliRunner
-from mock import DEFAULT, patch
 from requests.exceptions import HTTPError
 
 from scripts.user_retirement.get_learners_to_retire import get_learners_to_retire

scripts/user_retirement/tests/test_retire_one_learner.py

@@ -1,9 +1,9 @@
 """
 Test the retire_one_learner.py script
 """
+from unittest.mock import DEFAULT, patch
 
 from click.testing import CliRunner
-from mock import DEFAULT, patch
 
 from scripts.user_retirement.retire_one_learner import (
     END_STATES,

scripts/user_retirement/tests/test_retirement_archive_and_cleanup.py

@@ -4,12 +4,12 @@ Test the retirement_archive_and_cleanup.py script
 
 import datetime
 import os
+from unittest.mock import DEFAULT, call, patch
 
 import boto3
 import pytest
 from botocore.exceptions import ClientError
 from click.testing import CliRunner
-from mock import DEFAULT, call, patch
 from moto import mock_ec2, mock_s3
 
 from scripts.user_retirement.retirement_archive_and_cleanup import (

scripts/user_retirement/tests/test_retirement_bulk_status_update.py

@@ -1,9 +1,9 @@
 """
 Test the retirement_bulk_status_update.py script
 """
+from unittest.mock import DEFAULT, patch
 
 from click.testing import CliRunner
-from mock import DEFAULT, patch
 
 from scripts.user_retirement.retirement_bulk_status_update import (
     ERR_BAD_CONFIG,

scripts/user_retirement/tests/test_retirement_partner_report.py

@@ -8,9 +8,9 @@ import os
 import time
 import unicodedata
 from datetime import date
+from unittest.mock import DEFAULT, patch
 
 from click.testing import CliRunner
-from mock import DEFAULT, patch
 from six import PY2, itervalues
 
 from scripts.user_retirement.retirement_partner_report import \

scripts/user_retirement/tests/utils/test_edx_api.py

@@ -2,12 +2,12 @@
 Tests for edX API calls.
 """
 import unittest
+from unittest.mock import DEFAULT, patch
 from urllib.parse import urljoin
 
 import requests
 import responses
 from ddt import data, ddt, unpack
-from mock import DEFAULT, patch
 from requests.exceptions import ConnectionError, HTTPError
 from responses import GET, PATCH, POST, matchers
 from responses.registries import OrderedRegistry

scripts/user_retirement/tests/utils/test_jenkins.py

@@ -6,11 +6,11 @@ import json
 import re
 import unittest
 from itertools import islice
+from unittest.mock import Mock, call, mock_open, patch
 
 import backoff
 import ddt
 import requests_mock
-from mock import Mock, call, mock_open, patch
 
 import scripts.user_retirement.utils.jenkins as jenkins
 from scripts.user_retirement.utils.exception import BackendError

scripts/user_retirement/tests/utils/thirdparty_apis/test_salesforce.py

@@ -3,8 +3,8 @@ Tests for the Salesforce API functionality
 """
 import logging
 from contextlib import contextmanager
+from unittest import mock
 
-import mock
 import pytest
 from simple_salesforce import SalesforceError
 

scripts/user_retirement/tests/utils/thirdparty_apis/test_segment_api.py

@@ -2,8 +2,8 @@
 Tests for the Segment API functionality
 """
 import json
+from unittest import mock
 
-import mock
 import pytest
 import requests
 from six import text_type