title: ModuleNotFoundError when attempting to import from outside of directory
body: <p>I'm working on a Flask app and attempting to run my test file but unable to do so. My current app structure is:</p>
  
  <pre><code>Project
  ── app
  │   ├── __init__.py
  │   ├── forms.py
  │   ├── model.py
  │   ├── models.py
  │   ├── static
  │   │   ├── css
  │   │   ├── fonts
  │   │   ├── img
  │   │   ├── js
  │   │   └── uploads
  │   ├── templates
  │   │   ├── client
  │   │   │   ├── client-base.html
  │   │   │   ├── client-inventory.html
  │   │   │   ├── client-login.html
  │   │   │   ├── client-macros.html
  │   │   │   ├── client-main.html
  │   │   │   └── client-signup.html
  │   │   └── user
  │   │       ├── user-base.html
  │   │       ├── user-macros.html
  │   │       └── user-main.html
  │   └── views
  │       ├── __init__.py
  │       ├── client.py
  │       └── user.py
  ├── config.py
  ├── run.py
  └── tests
      └── test_user_model.py
  </code></pre>
  
  <p>when I attempt to run <code>from app.models import User</code> in <code>test_user_model.py</code> it raises <code>ModuleNotFoundError: No module named 'app'</code>. I've tried editing the import statement countless different ways but it still raises an error in every case (<code>from ..app import models</code> is out of scope, <code>import app</code> and similar imports also don't work.)</p>