AFNetworking 打印错误信息(二进制信息)
NSError *underError = error.userInfo[@"NSUnderlyingError"];
NSData *data = underError.userInfo[AFNetworkingOperationFailingURLResponseDataErrorKey];
NSString *errorStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
CXLog(@"%@", errorStr);