def temporary_mutation(obj, **kwargs):
    """Temporarily change object attribute.

    Temporarily set the attr on a particular object to a given value then
    revert when finished.

    One use of this is to temporarily set the read_deleted flag on a context
    object:

        with temporary_mutation(context, read_deleted="yes"):
            do_something_that_needed_deleted_objects()
    """

    def is_dict_like(thing):
        return hasattr(thing, 'has_key')

    def get(thing, attr, default):
        if is_dict_like(thing):
            return thing.get(attr, default)
        else:
            return getattr(thing, attr, default)

    def set_value(thing, attr, val):
        if is_dict_like(thing):
            thing[attr] = val
        else:
            setattr(thing, attr, val)

    def delete(thing, attr):
        if is_dict_like(thing):
            del thing[attr]
        else:
            delattr(thing, attr)

    NOT_PRESENT = object()

    old_values = {}
    for attr, new_value in kwargs.items():
        old_values[attr] = get(obj, attr, NOT_PRESENT)
        set_value(obj, attr, new_value)

    try:
        yield
    finally:
        for attr, old_value in old_values.items():
            if old_value is NOT_PRESENT:
                delete(obj, attr)
            else:
                set_value(obj, attr, old_value)