cairographics.org DNS is unreliable
Moving from cairo/cairo#828 (closed), cairographics.org seems to have unreliable DNS. For example:
[00:00:00] FAILURE [8c526386] core-deps/cairomm.bst: tar source at core-deps/cairomm.bst [line 4 column 2]: Error mirroring https://cairographics.org/releases/cairomm-1.18.0.tar.xz: <urlopen error [Errno -5] No address associated with hostname>
This has been ongoing for at least a month now but probably longer.