Currently creating tar, gztar, bztar source distributions using the
"--formats=tar,gztar,bztar" distutils option requires external utilities
(tar and possibly one of gzip, bzip2, or compress) to be installed on
the system since distutils uses them.
This is not a problem on most UNIX systems which provide these utilities
by default.  On all other systems (e.g. Windows) it is required to
install such utilities separately and have the executables available in
a directory on your PATH in order to have them work.

I discussed this on distutils mailing list [1] and tried to fix this
hassle. 
The patch in attachment permit to use the distutils
"--formats=tar,gztar,bztar" option without need of having tar/gzip/bzip2
utilities installed by using the tarfile module instead of os.spawn().
It also fixes bug #1885 [2].


[1] http://mail.python.org/pipermail/distutils-sig/2008-January/008654.html
[2] http://bugs.python.org/issue1885