Fix test for Python 2.7 on windows

Author: dflook

test/test_prefer_single_line.py

@@ -157,7 +157,7 @@ def test_unparse_prefer_single_line_true():
 def test_cli_default_uses_newlines():
     """CLI without --prefer-single-line uses newlines."""
     code = 'a = 1\nb = 2\nc = 3'
-    expected = 'a=1\nb=2\nc=3'
+    expected = os.linesep.join(['a=1', 'b=2', 'c=3'])
 
     with tempfile.NamedTemporaryFile(mode='w', suffix='.py', delete=False) as f:
         f.write(code)