You're looking at StableBuild's Deleted PyPI mirror - where we index all deleted packages from the Python package registry.

rasa-sdk
3.8.0a1

This version was deleted from PyPI around 2023-12-19. Installing fails with:
$ pip3 install rasa-sdk==3.8.0a1 ERROR: Could not find a version that satisfies the requirement rasa-sdk==3.8.0a1
View other deleted versions of rasa-sdk

Install through StableBuild

You can install this package from StableBuild's PyPI snapshots from before the version was deleted:
pip3 install \ -i https://YOUR_API_KEY.pypimirror.stablebuild.com/2023-12-18/ \ rasa-sdk==3.8.0a1
Sign up for StableBuild to get an API key (it's free and takes <60 seconds!)

Or, download files manually

And install manually via pip:
rasa_sdk-3.8.0a1-py3-none-any.whl (44.2KB)
rasa_sdk-3.8.0a1.tar.gz (33.6KB)