title: Python: defaultdict became unmarshallable object in 2.6?
body: <p>Did defaultdict's become not marshal'able as of Python 2.6? The following works under 2.5, fails under 2.6 with "ValueError: unmarshallable object" on OS X 1.5.6, python-2.6.1-macosx2008-12-06.dmg from python.org:</p>
  
  <pre><code>from collections import defaultdict
  import marshal
  dd = defaultdict(list)
  marshal.dump(dd, file('/tmp/junk.bin','wb') )
  </code></pre>