Code review comment for lp:~mew/charm-helpers/fetchallthethings

Deploying a tar file seems to fail:

root@liam-lxc-charmhelper-0:/var/lib/juju/units/charmhelper-0/charm/lib/charmhelper# mkdir /var/lib/juju/units/charmhelper-0/charm/fetched
root@liam-lxc-charmhelper-0:/var/lib/juju/units/charmhelper-0/charm/lib/charmhelper# python
Python 2.7.3 (default, Apr 10 2013, 05:46:21)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import charmhelpers.fetch.archiveurl
>>> fh = charmhelpers.fetch.archiveurl.ArchiveUrlFetchHandler()
>>> fh.can_handle('file:///tmp/payload.tar')
True
>>> fh.install('file:///tmp/payload.tar')
Unit name is not defined
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "charmhelpers/fetch/archiveurl.py", line 43, in install
    return extract(dld_file)
  File "charmhelpers/payload/archive.py", line 41, in extract
    get_archive_handler(archive_name)(archive_name, destpath)
  File "charmhelpers/payload/archive.py", line 49, in extract_tarfile
    archive = tarfile.open(archive_name)
  File "/usr/lib/python2.7/tarfile.py", line 1660, in open
    return func(name, "r", fileobj, **kwargs)
  File "/usr/lib/python2.7/tarfile.py", line 1722, in gzopen
    fileobj = bltn_open(name, mode + "b")
IOError: [Errno 21] Is a directory: '/var/lib/juju/units/charmhelper-0/charm/fetched/payload.tar'
>>>