errorhandler:
in the event of some abnormality, such as 404, 500, if you want to customize handle these errors can be processed using errorhandler using errorhandler points to note:
1. In errorhandler decorative hook function, to return the corresponding status code
2. errorhandler decorative hook function, it is necessary to write a position parameter, for receiving an error message, if there is no writing position parameter, an error is reported
3. flask.abort manually throw some errors, such parameters are found when the problem, you can manually throw a 400 error, and then let the good defined 400 error handling logic to handle
500 error
404 Error
abort conjunction with errorhandler
