Api server issue

/usr/lib/python2.7/dist-packages/pycassa/marshal.py in pack_bytes(v=None, _=None)
  317                 raise TypeError("A str or unicode value was expected, " +
  318                                 "but %s was received instead (%s)"
  319                                 % (v.__class__.__name__, str(v)))
  320             return v
  321         return pack_bytes
v = None
v.__class__ = <type 'NoneType'>
v.__class__.__name__ = 'NoneType'
builtinstr = <type 'str'>
<type 'exceptions.TypeError'>: A str or unicode value was expected, but NoneType was received instead (None)
    __class__ = <type 'exceptions.TypeError'>
    __delattr__ = <method-wrapper '__delattr__' of exceptions.TypeError object>
    __dict__ = {}
    __doc__ = 'Inappropriate argument type.'
    __format__ = <built-in method __format__ of exceptions.TypeError object>
    __getattribute__ = <method-wrapper '__getattribute__' of exceptions.TypeError object>
    __getitem__ = <method-wrapper '__getitem__' of exceptions.TypeError object>
    __getslice__ = <method-wrapper '__getslice__' of exceptions.TypeError object>
    __hash__ = <method-wrapper '__hash__' of exceptions.TypeError object>
    __init__ = <method-wrapper '__init__' of exceptions.TypeError object>
    __new__ = <built-in method __new__ of type object>
    __reduce__ = <built-in method __reduce__ of exceptions.TypeError object>
    __reduce_ex__ = <built-in method __reduce_ex__ of exceptions.TypeError object>
    __repr__ = <method-wrapper '__repr__' of exceptions.TypeError object>
    __setattr__ = <method-wrapper '__setattr__' of exceptions.TypeError object>
    __setstate__ = <built-in method __setstate__ of exceptions.TypeError object>
    __sizeof__ = <built-in method __sizeof__ of exceptions.TypeError object>
    __str__ = <method-wrapper '__str__' of exceptions.TypeError object>
    __subclasshook__ = <built-in method __subclasshook__ of type object>
    __unicode__ = <built-in method __unicode__ of exceptions.TypeError object>
    args = ('A str or unicode value was expected, but NoneType was received instead (None)',)
    message = 'A str or unicode value was expected, but NoneType was received instead (None)'

The above is a description of an error in a Python program.  Here is
the original traceback:

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_cfg_api_server.py", line 1569, in handler_trap_exception
    (ok, status) = self._rbac.validate_request(get_request())
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_rbac.py", line 231, in validate_request
    rule_list = self.get_rbac_rules(request)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_rbac.py", line 144, in get_rbac_rules
    rules = self.get_rbac_rules_object('project', project_id)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_rbac.py", line 80, in get_rbac_rules_object
    (ok, result) = self._db_conn.dbe_read(obj_type, obj_uuid, obj_fields)
  File "/usr/lib/python2.7/dist-packages/vnc_cfg_api_server/vnc_db.py", line 1090, in dbe_read
    obj_type, [obj_id], obj_fields, ret_readonly=ret_readonly)
  File "/usr/lib/python2.7/dist-packages/cfgm_common/vnc_cassandra.py", line 472, in wrapper
    return func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/cfgm_common/vnc_cassandra.py", line 780, in object_read
    timestamp=True)
  File "/usr/lib/python2.7/dist-packages/cfgm_common/vnc_cassandra.py", line 207, in multiget
    column_count=self._MAX_COL)
  File "/usr/lib/python2.7/dist-packages/cfgm_common/vnc_cassandra.py", line 472, in wrapper
    return func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/pycassa/columnfamily.py", line 761, in multiget
    packed_keys = map(self._pack_key, keys)
  File "/usr/lib/python2.7/dist-packages/pycassa/columnfamily.py", line 488, in _pack_key
    return self._key_packer(key)
  File "/usr/lib/python2.7/dist-packages/pycassa/marshal.py", line 319, in pack_bytes
    % (v.__class__.__name__, str(v)))
TypeError: A str or unicode value was expected, but NoneType was received instead (None)