Close file descriptor properly.

Stop py.test complaining.

tests/test_diceware.py

@@ -53,6 +53,7 @@ class TestHandleOptions(object):
         options = handle_options(['mywords', ])
         assert options.infile is not None
         assert options.infile.read() == 'one\ntwo\n'
+        options.infile.close()
 
     def test_handle_options_version(self):
         # we can ask for version infos