Use unittest.mock instead of mock (#469)

.github/workflows/tests.yaml

@@ -25,7 +25,7 @@ jobs:
           TESTDB: actions.cnf
         run: |
           pip install -U pip
-          pip install -U mock coverage pytest pytest-cov
+          pip install -U coverage pytest pytest-cov
           pip install .
           pytest --cov ./MySQLdb
       - uses: codecov/codecov-action@v1

tests/test_MySQLdb_times.py

@@ -1,11 +1,11 @@
-import mock
-import unittest
-from time import gmtime
 from datetime import time, date, datetime, timedelta
+from time import gmtime
+import unittest
+from unittest import mock
+import warnings
 
 from MySQLdb import times
 
-import warnings
 
 warnings.simplefilter("ignore")