bug#21784: cannot install icecat!

[-=}\*/{=-]

starting download of
`/gnu/store/0d7xnp3nji2mi4cw4jmd3mzbpija9a5a-xz-5.0.4.tar.gz' from `
http://tukaani.org/xz/xz-5.0.4.tar.gz'...
ERROR: download failed "http://tukaani.org/xz/xz-5.0.4.tar.gz"; 403
"Forbidden"
failed to download
"/gnu/store/0d7xnp3nji2mi4cw4jmd3mzbpija9a5a-xz-5.0.4.tar.gz" from "
http://tukaani.org/xz/xz-5.0.4.tar.gz";
builder for
`/gnu/store/1y6b3ar37ff4q16714m77d56giv01cr5-xz-5.0.4.tar.gz.drv' failed to
produce output path
`/gnu/store/0d7xnp3nji2mi4cw4jmd3mzbpija9a5a-xz-5.0.4.tar.gz'