Rename refactoring allow the use of Python keywords

[researcher175]

Rename refactoring is successfully executed using any Python keyword in B.text.

Steps to reproduce the behavior:

1. Code before refactoring:

class B:

    def a(self) -> None:
        text = 'hello'

2. Apply the Rename refactoring to the variable "text"

3. Expected to Rope emit an error due to the use of a Python keyword.

[lieryan]

Adding a validation here makes sense to me. It seems like it should be fairly straightforward to add validation here in rename.py to validate that new_name should be checked against keyword.iskeyword().

Would you want to take a bite at implementing this?