I believe this package will have breaking incompatibilities with Python 3.9 due to the deprecation of importing directly from collections.

The change seems pretty simple. It just requires updating py3k_compat.py to use collections.abc.Callable instead of collections.Callable.

c:\python38\lib\site-packages\pyreadline\py3k_compat.py:8
DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and in 3.9 it will stop working