Multiple assignment operation returns object is not iterable

I have no idea what this means:

(success, admin_id) = login(email, password)

The login method looks something like this:

def login(email, password):
    try:
        user = db.session.query(Admin).filter_by(email=email).first()        

        valid_role = 'Admin'

        if valid_role in user.role:       
            return user
    except Exception as e:
        print e

    return None

It returns either a TypeError: 'Admin' object is not iterable or a ValueError: too many values to unpack when I try to return just the user.id. Thank you for any help.