Ubuntu 導入IMageGrab 出錯，解決方法

	from PIL  import ImageGrab

功能：ImageGrab模塊能將屏幕或剪切板的內容複製到PIL圖像內存。
The ImageGrab module can be used to copy the contents of the screen or the clipboard to a PIL image memory.
問題：The current version works on macOS and Windows only.
解決方法：使用pyscreenshot庫，它是Linux系統的ImageGrab替代品

    import pyscreenshot as ImageGrab

參考博客：
http://www.pythonheidong.com/blog/article/145595/
https://pillow.readthedocs.io/en/stable/reference/ImageGrab.html