Getting the below error when trying to install the module document_webdav_old

Hi,
Am getting the below error when trying to install the module document_webdav_old.
Am using the
Version 5.0.9

Traceback (most recent call last):
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/netsvc.py", line 245, in dispatch
    result = LocalService(service_name)(method, *params)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/netsvc.py", line 74, in __call__
    return getattr(self, method)(*params)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/service/web_services.py", line 632, in execute
    return self._execute(db, uid, wiz_id, datas, action, context)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/service/web_services.py", line 612, in _execute
    return wiz.execute(db, uid, self.wiz_datas[wiz_id], action, context)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/wizard/__init__.py", line 178, in execute
    res = self.execute_cr(cr, uid, data, state, context)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/wizard/__init__.py", line 73, in execute_cr
    action_res = action(self, cr, uid, data, context)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/addons/base/module/wizard/wizard_module_upgrade.py", line 92, in _upgrade_module
    db, pool = pooler.restart_pool(cr.dbname, update_module=True)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/pooler.py", line 62, in restart_pool
    return get_db_and_pool(db_name, force_demo, status, update_module=update_module)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/pooler.py", line 40, in get_db_and_pool
    addons.load_modules(db, force_demo, status, update_module)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/addons/__init__.py", line 740, in load_modules
    r = load_module_graph(cr, graph, status, report=report)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/addons/__init__.py", line 581, in load_module_graph
    register_class(package.name)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/addons/__init__.py", line 403, in register_class
    imp.load_module(m, *fm)
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/addons/document_webdav_old/__init__.py", line 29, in <module>
    import document
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/addons/document_webdav_old/document.py", line 29, in <module>
    from webdav.content_index import content_index
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/addons/document_webdav_old/webdav/__init__.py", line 1, in <module>
    import webdav_server
  File "/usr/local/lib/python2.6/dist-packages/openerp-server/addons/document_webdav_old/webdav/webdav_server.py", line 5, in <module>
    from xml.dom import ext
ImportError: cannot import name ext