Tarfile seem to get filenames wrong, at least some times, at least on 
MacOSX. As an example, take the attached tar file (a distutils bdist-
dumb for OSX) and do 

>>> tf = tarfile.open(..., 'r')
>>> print tf.getnames()

Notice how for many filenames an initial bit of the pathname is 
missing.

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There's no uploaded file!  You have to check the
checkbox labeled "Check to Upload & Attach File"
when you upload a file.

Please try again.

(This is a SourceForge annoyance that we can do
nothing about. :-( )

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Actually, I did check the box (just this once:-) but sourceforge refused the 
file, probably too big. It can be found at <http://www.cwi.nl/~jack/pimp/
Numeric-22.0.darwin-6.3-Power_Macintosh.tar.gz>.

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After some digging the problem turns out that the prefix field in the file 
header is not completely zero-filled, the very last byte is a '('. Your code 
specifically checks for it being zero-filled. However, if I look up the tar 
standard (www.opengroup.org, unix standard, utilities, pax, somewhere half 
way down is the ustar file format standard) it says the data in the prefix field 
is NUL-terminated, it says nothing about having to be NUL-filled
.

A possible fix would be to simply take prefix up to the first NUL, but I'm 
contacting Lars first to see if he has an opinion.

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Fixed in tarfile.py ref 1.8