Error raised from Flask app is logged as successful function execution

[paulbatum]

If you write a python function using the WSGI support and then raise an error from the flask app, the error is not reported correctly.

Steps to reproduce:

1. Make a function app that uses flask with the WSGI support
2. Use something like this:

__init__.py:

import logging

import azure.functions as func
from api.app import application

def main(req: func.HttpRequest, context: func.Context) -> func.HttpResponse:    
    return func.WsgiMiddleware(application).handle(req, context)    

app.py:

from flask import Flask
from flask_restful import reqparse, Resource, Api

application = Flask(__name__)
api = Api(application)

class Stores(Resource):
    def get(self):     
        raise Exception('server error')

requirements.txt:

aniso8601==9.0.1
click==8.0.1
colorama==0.4.4
Flask==2.0.1
Flask-RESTful==0.3.9
itsdangerous==2.0.1
Jinja2==3.0.1
MarkupSafe==2.0.1
pytz==2021.1
six==1.16.0
Werkzeug==2.0.1

3. Invoke the function. If running locally, you'll get output like this:

Note that in the last line, we say the function succeeded. This is incorrect because the server raised an error. The client gets the response as a 500, so there is no problem with how the response is handled. But any metrics regarding function failures will be thrown out by treating this as a success.

Its possible there are similar issues in this area. I suggest a thorough check of how error cases are handled by the WSGI handler.