Having had another look at the description on the setup-python action, I think we are going to need to tell it what files to use to control the cache?

Input cache-dependency-path is used for cases when multiple dependency files are used, they are located in different subdirectories or different files for the hash that want to be used.

Although i don't know what files sunpy would use to control the cache as it would need updating regularly to catch the newest files and we don't have a pins file?

Yeah, I wonder if it's easiest for users of this action to do this manually using the caching arguments already present? At least this PR isn't a general enough approach, so I'll close.