Revoke token intermittently dumps stacktrace - Icehouse M3

Revoke token intermittently dumps stack trace. I don't see "remove" method in RevokeTree object. May be I'm missing something

(keystone.common.wsgi): 2014-03-20 03:17:55,054 ERROR 'RevokeTree' object has no attribute 'remove'
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/keystone/common/wsgi.py", line 205, in __call__
    result = method(context, **params)
  File "/usr/lib/python2.7/dist-packages/keystone/auth/controllers.py", line 316, in authenticate_for_token
    self.authenticate(context, auth_info, auth_context)
  File "/usr/lib/python2.7/dist-packages/keystone/auth/controllers.py", line 416, in authenticate
    auth_context)
  File "/usr/lib/python2.7/dist-packages/keystone/auth/plugins/token.py", line 39, in authenticate
    response = self.provider.validate_token(token_id)
  File "/usr/lib/python2.7/dist-packages/keystone/token/provider.py", line 118, in validate_token
    self._is_valid_token(token)
  File "/usr/lib/python2.7/dist-packages/keystone/token/provider.py", line 227, in _is_valid_token
    self.check_revocation(token)
  File "/usr/lib/python2.7/dist-packages/keystone/token/provider.py", line 156, in check_revocation
    return self.check_revocation_v3(token)
  File "/usr/lib/python2.7/dist-packages/keystone/token/provider.py", line 149, in check_revocation_v3
    self.revoke_api.check_token(token_values)
  File "/usr/lib/python2.7/dist-packages/keystone/contrib/revoke/core.py", line 190, in check_token
    self._cache.synchronize_revoke_map(self.driver)
  File "/usr/lib/python2.7/dist-packages/keystone/contrib/revoke/core.py", line 79, in synchronize_revoke_map
    self.revoke_map.remove(e)
AttributeError: 'RevokeTree' object has no attribute 'remove'