Handling exceptions

In RESTful applications, Flask allows the endpoint function to trigger error handlers that return error messages in JSON format. The following snippets are the error handlers of our ch03 application:

@app.errorhandler(404)
def not_found(e):
    return jsonify(error=str(e)), 404
@app.errorhandler(400)
def bad_request(e):
    return jsonify(error=str(e)), 400
def server_error(e):
    print(e)
    return jsonify(error=str(e)), 500
app.register_error_handler(500, server_error)

Error handlers can also return the JSON response through the jsonify(), make_response(), or Response class. As shown in the given error handlers, the implementation is the same with the web-based error handlers except for the jsonify() method, which serializes the captured error message to the JSON type instead of using render_template().

Custom exception classes must include both the HTTP Status Code and error...