flask和werkzurg的版本冲突，在这里也贴上解决方法，供后面踩坑的小伙伴参考：
报错：AttributeError: 'Request' object has no attribute 'is_xhr'
解决：The Werkzeug library (dependency from Flask) recently received a major update (0.16.1 --> 1.0.0) and it looks like Flask (<=0.12.4) does not restrict it.
You have 2 options:
Stick with your current version of Flask and restrict the Werkzeug version that is fetched explicitly in your application's setup.py or requirements.txt (werkzeug<1.0)
Upgrade to a recent version of Flask (>=1.0.0), whichis running fine with latest Werkzeug