Using decorator @functions_framework.errorhandler makes the python script impossible to import #136

Using decorator @functions_framework.errorhandler makes the python script impossible to import without creating an application.
Import produces the error:

AttributeError: module 'functions_framework' has no attribute 'errorhandler'

Example

Trying to start run 'importer.py' script produce the above error.

decorated.py

from typing import Tuple

from flask.typing import ResponseValue, StatusCode

import functions_framework


@functions_framework.errorhandler
def handle_exception(ex: Exception) -> Tuple[ResponseValue[str], StatusCode]:
    return "Unhandled exception", 500

importer.py

import decorated

if __name__ == '__main__':
    print("Imported")

Possible source of the issue

The error handler decorator is registered in functions_framework.create_app() and it is not available without calling this functons.