bzr commit raises a weird conflict

[Bastien]

I wanted to push a tiny docstring bugfix (bug#14163) but could not.

"~$ bzr commit" complains about a conflict.

"~$ bzr conflicts" yields:
  Conflict: can't delete leim/ja-dic because it is not empty.  Not deleting.

I first ran "~$ make maintainer-clean" before trying to commit,
because I did build Emacs from this directory.

How can I resolve this "conflict"?

I know it safer to build from a dedicated branch, and to use a clean
branch for commits, but still, I don't understand what's wrong.

Thanks for any help,

-- 
 Bastien