Remove reference to Mock

Since Python 3.3, unittest.mock has been part of the standard library

requirements-dev.txt

@@ -1,4 +1,3 @@
-mock>=1.3.0
 sh>=1.11
 parameterized>=0.6.1
 pytest

test/cwd_test.py

@@ -1,5 +1,5 @@
 import unittest
-import mock
+from unittest import mock
 import os
 import tempfile
 import shutil

test/segments_test/bzr_test.py

@@ -1,7 +1,7 @@
 import unittest
 from contextlib import ExitStack
 
-import mock
+from unittest import mock
 import tempfile
 import shutil
 import sh

test/segments_test/fossil_test.py

@@ -2,7 +2,7 @@
 from contextlib import ExitStack
 from os import environ
 
-import mock
+from unittest import mock
 import tempfile
 import shutil
 import sh

test/segments_test/git_stash_test.py

@@ -1,7 +1,7 @@
 import unittest
 from contextlib import ExitStack
 
-import mock
+from unittest import mock
 import tempfile
 import shutil
 import sh

test/segments_test/git_test.py

@@ -1,7 +1,7 @@
 import unittest
 from contextlib import ExitStack
 
-import mock
+from unittest import mock
 import tempfile
 import shutil
 import sh

test/segments_test/hg_test.py

@@ -1,7 +1,7 @@
 import unittest
 from contextlib import ExitStack
 
-import mock
+from unittest import mock
 import tempfile
 import shutil
 import sh

test/segments_test/hostname_test.py

@@ -1,5 +1,5 @@
 import unittest
-import mock
+from unittest import mock
 import powerline_shell.segments.hostname as hostname
 from powerline_shell.themes.default import Color
 from argparse import Namespace

test/segments_test/svn_test.py

@@ -3,7 +3,7 @@
 import shutil
 from contextlib import ExitStack
 
-import mock
+from unittest import mock
 import sh
 import powerline_shell.segments.svn as svn
 from ..testing_utils import dict_side_effect_fn

test/segments_test/uptime_test.py

@@ -1,5 +1,5 @@
 import unittest
-import mock
+from unittest import mock
 import powerline_shell.segments.uptime as uptime
 
 test_cases = {