expected string or Unicode object, NoneType found

[tablecell]

import sys  
sys.path.append('.')  
import ctypes
ctypes.windll.LoadLibrary(r"c:\python27\audio\libopusfile-0.dll")

import pyaudio
from opus import encoder, decoder

Traceback (most recent call last):
File "a.py", line 8, in
from opus import encoder, decoder
File "build\bdist.win32\egg\opus\encoder.py", line 3, in
File "build\bdist.win32\egg\opus\api__init__.py", line 5, in
# package placeholder
File "C:\PYTHON27\lib\ctypes__init__.py", line 353, in init
self._handle = _dlopen(self._name, mode)
TypeError: expected string or Unicode object, NoneType found