[meld] Update test imports for Python 3

[Kai Willadsen <kaiw src gnome org>]

commit 00bfc6d4fa852d57d5bcf7d000c3284800a16236
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sun Feb 19 09:09:07 2017 +1000

    Update test imports for Python 3

 test/test_filediff.py            |    4 ++--
 test/test_gutterrendererchunk.py |    3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/test/test_filediff.py b/test/test_filediff.py
index b998ff3..b0e5501 100644
--- a/test/test_filediff.py
+++ b/test/test_filediff.py
@@ -1,7 +1,7 @@
 
-import pytest
+from unittest import mock
 
-import mock
+import pytest
 from gi.repository import Gtk
 
 from meld.filediff import FileDiff
diff --git a/test/test_gutterrendererchunk.py b/test/test_gutterrendererchunk.py
index e101ee4..d0c0505 100644
--- a/test/test_gutterrendererchunk.py
+++ b/test/test_gutterrendererchunk.py
@@ -1,5 +1,6 @@
 
-import mock
+from unittest import mock
+
 import pytest
 
 import meld.gutterrendererchunk