Comment 6 for bug 703142

mterry, add one more to the list. Basically the same as benste's report in LP Bug #616482.

sciri@rico:~/Shredder$ apt-cache policy duplicity deja-dup
deja-dup:
  Installed: 18.1.1-0ubuntu1
  Candidate: 18.1.1-0ubuntu1
  Version table:
 *** 18.1.1-0ubuntu1 0
        500 http://archive.ubuntu.com/ubuntu/ natty/universe amd64 Packages
        100 /var/lib/dpkg/status
duplicity:
  Installed: 0.6.13-0ubuntu1
  Candidate: 0.6.13-0ubuntu1
  Version table:
 *** 0.6.13-0ubuntu1 0
        500 http://archive.ubuntu.com/ubuntu/ natty/universe amd64 Packages
        100 /var/lib/dpkg/status

Traceback (most recent call last):
  File "/usr/bin/duplicity", line 1262, in <module>
    with_tempdir(main)
  File "/usr/bin/duplicity", line 1255, in with_tempdir
    fn()
  File "/usr/bin/duplicity", line 1237, in main
    incremental_backup(sig_chain)
  File "/usr/bin/duplicity", line 479, in incremental_backup
    bytes_written = dummy_backup(tarblock_iter)
  File "/usr/bin/duplicity", line 161, in dummy_backup
    while tarblock_iter.next():
  File "/usr/lib/python2.7/dist-packages/duplicity/diffdir.py", line 505, in next
    result = self.process(self.input_iter.next(), size)
  File "/usr/lib/python2.7/dist-packages/duplicity/diffdir.py", line 187, in get_delta_iter
    for new_path, sig_path in collated:
  File "/usr/lib/python2.7/dist-packages/duplicity/diffdir.py", line 275, in collate2iters
    relem2 = riter2.next()
  File "/usr/lib/python2.7/dist-packages/duplicity/diffdir.py", line 344, in combine_path_iters
    refresh_triple_list(triple_list)
  File "/usr/lib/python2.7/dist-packages/duplicity/diffdir.py", line 330, in refresh_triple_list
    new_triple = get_triple(old_triple[1])
  File "/usr/lib/python2.7/dist-packages/duplicity/diffdir.py", line 316, in get_triple
    path = path_iter_list[iter_index].next()
  File "/usr/lib/python2.7/dist-packages/duplicity/diffdir.py", line 229, in sigtar2path_iter
    for tarinfo in tf:
  File "/usr/lib/python2.7/dist-packages/duplicity/tarfile.py", line 1211, in next
    tarinfo = self.tarfile.next()
  File "/usr/lib/python2.7/dist-packages/duplicity/tarfile.py", line 566, in next
    if tarinfo.issparse():
AttributeError: 'NoneType' object has no attribute 'issparse'