bzr: ERROR: This tree contains left-over files from a failed operation.

When I use Bazaar and Dropbox for version control system, I encounter a problem like "bzr: ERROR: This tree contains left-over files from a failed operation." when I retry to update the repository after network is down or similar thing stopping update.

The prompted solution is to delete files in the limbo folder which is under $PathofYourCodes\.bzr\checkout\. Currently the error still stays there even if you remove the whole limbo folder. In order to fix this issue, you should remove limbo and pending_deletion at the same time as they are sort of like associated folders.