[Mailman-Users] 3.0.0b1 fails bootstrap.py on Mountain Lion

[G B]

I'm installing Mailman for the first time, and chose to try the beta.  I'm installing on a Mountain Lion Server, that was cleanly installed.   I've since updated the OS to 10.8.1

I got as far as 'python bootstrap.py' and it failed immediately with the following traceback:

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Traceback (most recent call last):
  File "bootstrap.py", line 157, in <module>
    import pkg_resources
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/../../Extras/lib/python/pkg_resources.py", line 698, in <module>
    class Environment(object):
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/../../Extras/lib/python/pkg_resources.py", line 701, in Environment
    def __init__(self, search_path=None, platform=get_supported_platform(), python=PY_MAJOR):
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/../../Extras/lib/python/pkg_resources.py", line 99, in get_supported_platform
    plat = 'macosx-%s-%s' % ('.'.join(_macosx_vers()[:2]), m.group(3))
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/../../Extras/lib/python/pkg_resources.py", line 209, in _macosx_vers
    _cache.append(mac_ver()[0].split('.'))
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/platform.py", line 803, in mac_ver
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/platform.py", line 780, in _mac_ver_xml
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plistlib.py", line 78, in readPlist
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plistlib.py", line 406, in parse
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plistlib.py", line 418, in handleEndElement
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plistlib.py", line 452, in end_key
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plistlib.py", line 436, in getData
LookupError: unknown encoding: ascii
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FWIW, I can open an interactive Python session and execute "import pkg_resources"  from the command line without error.

Any ideas?

Thanks—
 Greg