Python 3.4 is not supported anymore.
It has been unsupported by the Python core team for a while now, its PyPI downloads are negligible, and our CI provider removed it as a supported option.

It's very unlikely that ``attrs`` will break under 3.4 anytime soon, which is why we do *not* block its installation on Python 3.4.
But we don't test it anymore and will block it once someone reports breakage.