We've done extensive testing on Debian stable live and never came across
this before. When you say you're testing this on Debian stable, do you
mean a locally build Debian stable image, or an officially released
Debian stable image?
Anyway, your trouble seems to begin because sudo is being removed,
presumably because it's somehow not marked as manually installed / or
just installed as a dependency for the live environment, so calamares
wants to remove it but it's configured to give error code 100 when a
root user isn't configured, see message after the following string:
Removing sudo (1.9.16p2-1) ...
Anyway, this doesn't at all seem like a bug in calamares. It's either in
the exact version of live-build you're using, or related to some
specific settings or meta-package.
-Jonathan
