ImageField is broken Django 2+

[wkleinheerenbrink]

The ImageField overrides the default Image widget. Since Django 2.1 the render() method for widgets has been changed, resulting in an error now.

"Support for Widget.render() methods without the renderer argument is removed."
https://docs.djangoproject.com/en/2.2/releases/2.1/#features-removed-in-2-1.

The override must be updated.