Get all form objects in a Django application

Here is what I want to do:

1. Retrieve a list of all objects in all my django apps that inherit from forma.Form
2. Find all CharField defined on the form
3. Verify that each of these fields has a max_length kwarg specified

My goal is the write a unit test to fail if a form exists within our system that does not have a max length specified.

how would I do this?