Import of `flask._compat` fails with Flask 2.0

[max-moser]

In the very recent 2.0 release of Flask 2.0, they dropped support for Python < 3.6. This includes the removal of the flask._compat module (https://github.com/pallets/flask/commit/662c245795c7cbb5dbd657a2d707c62c16770c18) Thus, the following import won't work anymore: https://github.com/klen/Flask-Collect/blob/develop/flask_collect/collect.py#L7