class _DiffCollectHandler:
    # ... other code
    def __call_(self, file, is_dir, base):
        # ... other code
        if file.endswitch(...
            with open(file) as diff:
                content = diff.read()
                self.output.write(self.DIFF_SEPARATOR)
                self.output.write(content)
                self.output.flush()
                # 不能再这里close self.output，这个函数会被反复调用，这里close，下次调用就会写入已经关闭的流了

    def close(self):
        self.output.close()

# 在下面的collect_diff_file函数中使用_DiffCollectHandler完毕后再关闭

def collect_diff_file(suite_dir):
    # ... other code
    if os.path.exists(result_result):
        handler = _DiffCollectionHandler(...)
        try:
            scan_path(result_dir, handler)
        finally:
            # 确保流一定会关闭
            handler.close()