download-for-sdist: command not found

[ph h]

Cloning into '/home/hph/sage-9.6/git/rc2/sage.mod/tmp/sage-9.6.rc2'...
done.
Updating files: 100% (9399/9399), done.
Enumerating objects: 841207, done.
Counting objects: 100% (841207/841207), done.
Delta compression using up to 8 threads
Compressing objects: 100% (801365/801365), done.
Writing objects: 100% (841207/841207), done.
Total 841207 (delta 671090), reused 160806 (delta 0)
Expanding reachable commits in commit graph: 104080, done.
Finished cloning Sage sources
/home/hph/sage-9.6/git/rc2/sage.mod/build/bin/sage-sdist: line 50: download-for-sdist: command not found