Fix PyPy

tests/trailing_whitespace_fixer_test.py

diff --git a/tests/trailing_whitespace_fixer_test.py b/tests/trailing_whitespace_fixer_test.py
index f698633..3b6a9a4 100644
--- a/tests/trailing_whitespace_fixer_test.py
+++ b/tests/trailing_whitespace_fixer_test.py
@@ -9,7 +9,8 @@
             ('foo.py', 'foo \nbar \n'),
             ('bar.py', 'bar\t\nbaz\t\n'),
         ):
-            open(filename, 'w').write(contents)
+            with open(filename, 'w') as f:
+                f.write(contents)  # pragma: no cover (python 2.6 coverage bug)
 
         ret = fix_trailing_whitespace(['foo.py', 'bar.py'])
         assert ret == 1