Delete bundle file of hg incoming in case of errors, preserve existing files. Let write_bundle always create the bundle file, check if target doesn't exist and delete it in case of errors. This way incoming only has to delete the bundle file if it was meant to be a temporary file.

# repo.py - repository base classes for mercurial
#
# Copyright 2005 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

class RepoError(Exception): pass