Gets a cached auth token

def get_cached_token(self):
        ''' Gets a cached auth token
        '''
        token_info = None
        if self.cache_path:
            try:
                f = open(self.cache_path)
                token_info_string = f.read()
                f.close()
                token_info = json.loads(token_info_string)

                if self.is_token_expired(token_info):
                    token_info = self.refresh_access_token(token_info['refresh_token'])

            except IOError:
                pass
        return token_info