Function local name binding from an outer scope

I need a way to "inject" names into a function from an outer code block, so they are accessible locally and they don't need to be specifically handled by the function's code (defined as function parameters, loaded from *args etc.)

The simplified scenario: providing a framework within which the users are able to define (with as little syntax as possible) custom functions to manipulate other objects of the framework (which are not necessarily global).

Ideally, the user defines

def user_func():
    Mouse.eat(Cheese)
    if Cat.find(Mouse):
        Cat.happy += 1

Here Cat, Mouse and Cheese are framework objects that, for good reasons, cannot be bounded to the global namespace.

I want to write a wrapper for this function to behave like this:

def framework_wrap(user_func):
    # this is a framework internal and has name bindings to Cat, Mouse and Cheese
    def f():
        inject(user_func, {'Cat': Cat, 'Mouse': Mouse, 'Cheese': Cheese})
        user_func()
    return f

Then this wrapper could be applied to all user-defined functions (as a decorator, by the user himself or automatically, although I plan to use a metaclass).

@framework_wrap
def user_func():

I am aware of the Python 3's nonlocal keyword, but I still consider ugly (from the framework's user perspective) to add an additional line:

nonlocal Cat, Mouse, Cheese

and to worry about adding every object he needs to this line.

Any suggestion is greatly appreciated.