See https://app.readthedocs.org/projects/python-lz4/builds/ - it appears to have been broken after f3462c8 and before (or at) 65b563a. The docs at https://python-lz4.readthedocs.io/en/stable/ still exist, but they're stuck at v4.3.2.
The project README also points to http://python-lz4.readthedocs.io/en/latest/ but this does not exist at all.
See https://app.readthedocs.org/projects/python-lz4/builds/ - it appears to have been broken after f3462c8 and before (or at) 65b563a. The docs at https://python-lz4.readthedocs.io/en/stable/ still exist, but they're stuck at v4.3.2.
The project README also points to http://python-lz4.readthedocs.io/en/latest/ but this does not exist at all.