-instance
  -config.py
-service
  -__init__.py
  -auth.py
  -db.py
  -tables.sql
-venv

class DefaultConfig(object):
    DEBUG = True
    TESTING = False
    SECRET_KEY = 'this-really-needs-to-be-changed'
    HOST       = "localhost"
    USER       = "root"
    PASSWD     = "hello"
    DB         = "testdb"

class ProductionConfig(DefaultConfig):
    DEBUG = False

import os
from flask import Flask

def create_app(config=None):
    # create and configure the app
    app = Flask(__name__, instance_relative_config=True)
    app.config.from_object('config.ProductionConfig')

    try:
        os.makedirs(app.instance_path)
    except OSError:
        pass

    from . import db
    db.init_app(app)

    from . import auth
    app.register_blueprint(auth.bp)

    return app

Debugged import:

- 'config' not found.

Original exception:

ModuleNotFoundError: No module named 'config'