Can't import some packages with odd paths

[James Westby]

Traceback (most recent call last):
  File "./import_package.py", line 364, in <module>
    sys.exit(main(*sys.argv[1:]))
  File "./import_package.py", line 351, in main
    import_package(package, distro, package_url)
  File "./import_package.py", line 327, in import_package
    update_db.import_package(local_dsc_path)
  File "plugins/builddeb/import_dsc.py", line 1715, in import_package
    upstream_part, upstream_md5)
  File "plugins/builddeb/import_dsc.py", line 1657, in _do_import_package
    upstream_md5)
  File "plugins/builddeb/import_dsc.py", line 1475, in import_upstream
    file_ids_from=upstream_trees + [self.tree])
  File "plugins/builddeb/import_dsc.py", line 161, in import_dir
    import_archive(tree, dir_file, file_ids_from=file_ids_from)
  File "plugins/builddeb/import_dsc.py", line 236, in import_archive
    trans_id = tt.trans_id_tree_path(relative_path)
  File "/usr/lib/python2.5/site-packages/bzrlib/transform.py", line 293, in trans_id_tree_path
    path = self.canonical_path(path)
  File "/usr/lib/python2.5/site-packages/bzrlib/transform.py", line 275, in canonical_path
    abs = self._tree.abspath(path)
  File "/usr/lib/python2.5/site-packages/bzrlib/workingtree.py", line 375, in abspath
    return pathjoin(self.basedir, filename)
  File "/usr/lib/python2.5/posixpath.py", line 65, in join
    path += '/' + b
UnicodeDecodeError: 'ascii' codec can't decode byte 0xed in position 1: ordinal not in range(128)

e.g.

scripts/failures/aspell-is
scripts/failures/aspell-ro
scripts/failures/git-core

This is related to bug 77657.