Index: fire-0.4.0/fire/core_test.py
===================================================================
--- fire-0.4.0.orig/fire/core_test.py	2020-04-03 19:14:51.000000000 +0200
+++ fire-0.4.0/fire/core_test.py	2022-03-16 13:48:27.568077390 +0100
@@ -22,7 +22,11 @@ from fire import core
 from fire import test_components as tc
 from fire import testutils
 from fire import trace
-import mock
+
+try:
+  import mock  # python 2.x
+except ModuleNotFoundError:
+  from unittest import mock  # python 3.x
 
 import six
 
Index: fire-0.4.0/fire/fire_import_test.py
===================================================================
--- fire-0.4.0.orig/fire/fire_import_test.py	2022-03-16 13:48:27.568077390 +0100
+++ fire-0.4.0/fire/fire_import_test.py	2022-03-16 13:51:27.561140579 +0100
@@ -18,7 +18,11 @@ import sys
 
 import fire
 from fire import testutils
-import mock
+
+try:
+  import mock  # python 2.x
+except ModuleNotFoundError:
+  from unittest import mock  # python 3.x
 
 
 class FireImportTest(testutils.BaseTestCase):
Index: fire-0.4.0/fire/fire_test.py
===================================================================
--- fire-0.4.0.orig/fire/fire_test.py	2020-12-17 01:20:39.000000000 +0100
+++ fire-0.4.0/fire/fire_test.py	2022-03-16 13:48:27.568077390 +0100
@@ -25,7 +25,10 @@ import fire
 from fire import test_components as tc
 from fire import testutils
 
-import mock
+try:
+  import mock  # python 2.x
+except ModuleNotFoundError:
+  from unittest import mock  # python 3.x
 import six
 
 
Index: fire-0.4.0/fire/interact_test.py
===================================================================
--- fire-0.4.0.orig/fire/interact_test.py	2022-03-16 13:48:27.568077390 +0100
+++ fire-0.4.0/fire/interact_test.py	2022-03-16 13:50:36.080836493 +0100
@@ -21,8 +21,10 @@ from __future__ import print_function
 from fire import interact
 from fire import testutils
 
-import mock
-
+try:
+  import mock  # python 2.x
+except ModuleNotFoundError:
+  from unittest import mock  # python 3.x
 
 try:
   import IPython  # pylint: disable=unused-import, g-import-not-at-top
Index: fire-0.4.0/fire/testutils.py
===================================================================
--- fire-0.4.0.orig/fire/testutils.py	2020-12-17 01:20:39.000000000 +0100
+++ fire-0.4.0/fire/testutils.py	2022-03-16 13:48:27.568077390 +0100
@@ -28,7 +28,10 @@ import unittest
 from fire import core
 from fire import trace
 
-import mock
+try:
+  import mock  # python 2.x
+except ModuleNotFoundError:
+  from unittest import mock  # python 3.x
 import six