[UI issue + BUG] recovering from rebase aborting due to untracked files

During an interactive rebase, it happened that some testing operations on
one commit created files that were normally added by a later commit,
leading to the following conflict:

$ git rebase --continue
error: Untracked working tree file 'xxxx' would be overwritten by merge. 
Aborting
Could not apply 8a2ea0a... L10n of photo and games.
$

No clue is given about what to do next.  It would be nice if one could
just removes the faulty files, and use "rebase --continue". 
Unfortunately, doing the following results in the rebase being prematurely
finished with success, with all patches starting with the one causing the
problem being silently dropped.

Now it is not so hard for an experienced user to rewind and avoid doing
the mistake a second time, but some safeguards would be nice.

Does anyone with knowledge of rebase internals see what goes wrong and how
to fix it best ?