如果我的输入json如下所示，我想引发一个异常：

{
"username":"user","password": ""
}

如果我将密码传递为null，那么我想引发一个异常。我可以知道棉花糖如何处理它。 我不想像下面这样显式检查：

request_jsn = request.get_json()
if 'password' in request_jsn.keys() :
   if request_jsn['password'] :
     password = request_jsn['password']

from marshmallow import Schema,fields
class UserSchema(Schema):
username = fields.String(required=True)
password = fields.String(required=True)
--------------
def post(self):

    if not request.json:
        return jsonify( {'msg':"Unsupported media type,Requests must be JSON",'code': 415})
    try:
       request_jsn =  Schema().load(request.get_json())
    except ValidationError as e:
        return jsonify(error_dict(current_request_id(),str(e),400))