Since this library is vendored by pip, which is itself vendored in CPython's ensurepip module, the fact that there's no release that includes PR #403 is blocking the removal of the deprecated abstract base classes from the collections module, long advertised as happening in Python 3.8, see python/cpython#10596

Normally I am the last person to ask for releases (I assume maintainers have good reasons for not doing so, and I usually don't like being on the receiving end of such requests), but the deadline for the 3.8 beta release is coming up very soon, so if there's any way to expedite an html5lib release it would really help that effort, and it would avoid stickier solutions like patching html5lib directly in pip.