The pyreadline is no longer actively maintained (last update of any kind was in 2015) and cannot work in Python 3.9+.
I think this caused pytest to fail running on Windows, since I searched pyreadline in pytest-dev and only this repository referenced pyreadline.
Consider use other packages instead (e.g. pyreadline3 or gnureadline), otherwise the user needs to fix manually like https://github.com/jlowin/fastmcp/blob/main/Windows_Notes.md.
Reference: