Make test_getoutput work on Windows.

Author: benjaminp

test_six.py

@@ -233,8 +233,8 @@ def test_map():
 
 def test_getoutput():
  from six.moves import getoutput
- output = getoutput('echo "foo"')
- assert output == 'foo'
+ output = getoutput('dir' if sys.platform.startswith('win') else 'echo foo')
+ assert output != ''
 
 
 def test_zip():