Hey here!
Thank you for the library!

Motivation

I'm using pydantic-extra-types as an optional dependency in my small library I will release soon.
I decided to test all types from pydanic-extra-types to verify that validation is successful.
But for S3Path the error was AttributeError instead of ValueError, that I (or any other pydantic user IMHO) would expect.

Changes

Refactor of S3Path init to raise ValueError and not AttributeError and tests that verify that on init (without using pydantic features) ValueError is raised. I also changed patt from str to Pattern for optimization