leap-seconds.list is no-longer supported by ieft.org

Attempting to download the leap-seconds.list file no longer works:

> python -m gpstime.leaps --help
...
RuntimeError: Error loading leap file https://www.ietf.org/timezones/data/leap-seconds.list: 404 Client Error: Not Found for url: https://www.ietf.org/timezones/data/leap-seconds.list

This is indeed confirmed by simply curling the same URL:

$ curl https://www.ietf.org/timezones/data/leap-seconds.list
ietf.org is no longer serving this file.

Can this be migrated to a new leap seconds provider?