No module named middleware.healthcheck

I follow the steps on http://swift.openstack.org/development_saio.html ,when i run "startmain",error is:
Starting proxy-server...(/etc/swift/proxy-server.conf)
container-server running (1153 - /etc/swift/container-server/1.conf)
container-server running (1154 - /etc/swift/container-server/2.conf)
container-server running (1155 - /etc/swift/container-server/3.conf)
container-server running (1156 - /etc/swift/container-server/4.conf)
container-server already started...
account-server running (1160 - /etc/swift/account-server/4.conf)
account-server running (1157 - /etc/swift/account-server/1.conf)
account-server running (1158 - /etc/swift/account-server/2.conf)
account-server running (1159 - /etc/swift/account-server/3.conf)
account-server already started...
object-server running (1161 - /etc/swift/object-server/1.conf)
object-server running (1162 - /etc/swift/object-server/2.conf)
object-server running (1163 - /etc/swift/object-server/3.conf)
object-server running (1164 - /etc/swift/object-server/4.conf)
object-server already started...
Traceback (most recent call last):
  File "/usr/local/bin/swift-proxy-server", line 7, in <module>
    execfile(__file__)
  File "/root/swift/bin/swift-proxy-server", line 22, in <module>

  File "/root/swift/swift/common/wsgi.py", line 123, in run_wsgi
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 247, in loadapp
    return loadobj(APP, uri, name=name, **kw)
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 271, in loadobj
    global_conf=global_conf)
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 296, in loadcontext
    global_conf=global_conf)
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 320, in _loadconfig
    return loader.get_context(object_type, name, global_conf)
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 450, in get_context
    global_additions=global_additions)
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 562, in _pipeline_app_context
    for name in pipeline[:-1]]
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 454, in get_context
    section)
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 476, in _context_from_use
    object_type, name=use, global_conf=global_conf)
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 406, in get_context
    global_conf=global_conf)
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 296, in loadcontext
    global_conf=global_conf)
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 328, in _loadegg
    return loader.get_context(object_type, name, global_conf)
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 620, in get_context
    object_type, name=name)
  File "/usr/lib/python2.7/dist-packages/paste/deploy/loadwsgi.py", line 646, in find_egg_entry_point
    possible.append((entry.load(), protocol, entry.name))
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 1955, in load
    entry = __import__(self.module_name, globals(),globals(), ['__name__'])
ImportError: No module named middleware.healthcheck

How to resolve it ? Thanks for your help.