When adding a file to a TarFile instance using addfile(), if the file paths (name and arcname) are unicode strings, then a struct.error will the raised. Python versions prior to 2.5 do not show this behaviour.

Assuming the current directory has a file name 'mac.txt', here is an interactive session that shows the problem:

Python 2.5 (r25:51908, Apr 18 2007, 19:06:57)
[GCC 3.4.6 20060404 (Red Hat 3.4.6-3)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import tarfile
>>> t=tarfile.open('test.tar', 'w')
>>> i=t.gettarinfo(u'mac.txt', u'mac.txt')
>>> t.addfile(i, file(u'mac.txt', 'r'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.5/tarfile.py", line 1422, in addfile
    self.fileobj.write(tarinfo.tobuf(self.posix))
  File "/usr/lib/python2.5/tarfile.py", line 871, in tobuf
    buf = struct.pack("%ds" % BLOCKSIZE, "".join(parts))
  File "/usr/lib/python2.5/struct.py", line 63, in pack
    return o.pack(*args)
struct.error: argument for 's' must be a string