@@ -5,8 +5,6 @@
 # the BSD License: http://www.opensource.org/licenses/bsd-license.php
 
 import contextlib
-import re
-
 import io
 import logging
 import os
@@ -21,7 +19,7 @@
 import threading
 from collections import OrderedDict
 from textwrap import dedent
-import unittest.mock
+import mock
 
 from git.compat import (
     string_types,
@@ -62,6 +60,11 @@
 __all__ = ('Git',)
 
 
+@contextlib.contextmanager
+def nullcontext(enter_result=None):
+    yield enter_result
+
+
 # ==============================================================================
 ## @name Utilities
 # ------------------------------------------------------------------------------
@@ -756,7 +759,7 @@ def execute(self, command,
                 cmd_not_found_exception = FileNotFoundError  # NOQA # exists, flake8 unknown @UndefinedVariable
             else:
                 cmd_not_found_exception = OSError
-            patch_caller_env = contextlib.nullcontext()
+            patch_caller_env = nullcontext()
         # end handle
 
         stdout_sink = (PIPE
@@ -781,7 +784,7 @@ def execute(self, command,
                     close_fds=is_posix,  # unsupported on windows
                     universal_newlines=universal_newlines,
                     creationflags=PROC_CREATIONFLAGS,
-                    **subprocess_kwargs,
+                    **subprocess_kwargs
                 )
         except cmd_not_found_exception as err:
             raise GitCommandNotFound(command, err)
 
@@ -4,12 +4,16 @@
 #
 # This module is part of GitPython and is released under
 # the BSD License: http://www.opensource.org/licenses/bsd-license.php
+from __future__ import print_function
+
 import contextlib
 import os
 import shutil
 import subprocess
 import sys
-from tempfile import TemporaryDirectory, TemporaryFile
+from tempfile import TemporaryFile
+from backports.tempfile import TemporaryDirectory
+import six
 
 from git import (
     Git,
@@ -122,12 +126,13 @@ def test_it_executes_git_not_from_cwd(self):
             else:
                 # Create a shell script that doesn't do anything.
                 impostor_path = os.path.join(tmpdir, "git")
-                with open(impostor_path, mode="w", encoding="utf-8") as file:
+                with open(impostor_path, mode="w") as file:
                     print("#!/bin/sh", file=file)
                 os.chmod(impostor_path, 0o755)
 
             with _chdir(tmpdir):
-                self.assertRegex(self.git.execute(["git", "version"]), r"^git version\b")
+                # six.assertRegex(self.git.execute(["git", "version"]).encode("UTF-8"), r"^git version\b")
+                self.assertRegexpMatches(self.git.execute(["git", "version"]), r"^git version\b")
 
     def test_it_accepts_stdin(self):
         filename = fixture_path("cat_file_blob")
 
@@ -1 +1,2 @@
 gitdb2>=2,<3
+mock
@@ -4,5 +4,5 @@ coverage
 flake8
 nose
 tox
-mock; python_version=='2.7'
-pathlib2; python_version=='2.7'
+backports.tempfile
+six