Hi,
I am seeing some irregularities on the the tar files created using python.

Consider the attached script.
This is the output from the scripts:
```
  # gz
b'0f2eb7b3cac63267b1cf51d2bd5e3144f53cc5b172bbad3dccd5adf4ffb2d220  /tmp/py.gz\n'
9bde8fdb44d98c5a838a9fedaff6e66cd536d91022f8a64a6ecc514f38ce01af
b'e37c3d30ae3c12e872c6aade55ac0a40da8b3f357ce8ed77287bc9f8f024e587  /tmp/py.gz\n'
7ac976e3c94b90abff3c4138a2d153e9be9cc87e2b5a97baf2be95ca04029936

  # bz2
b'd04678e749491e4de1065d3f72ba66395d6bd8ffba3d6360ed9ca2c514586fd3  /tmp/py.bz2\n'
9aa293624df8c40f47614045602af41cc603ca92c97c94926296ef38396d6e3f
b'd04678e749491e4de1065d3f72ba66395d6bd8ffba3d6360ed9ca2c514586fd3  /tmp/py.bz2\n'
9aa293624df8c40f47614045602af41cc603ca92c97c94926296ef38396d6e3f

  # xz
b'a050baa1ab765fa037524ff061d59f62ad37bc6d1bacf98f9bff2f4b4c312fab  /tmp/py.xz\n'
ca39f034d7812d2420573218c69313ac31fd516ffebe1a57f4e41a32e1e840b9
b'a050baa1ab765fa037524ff061d59f62ad37bc6d1bacf98f9bff2f4b4c312fab  /tmp/py.xz\n'
ca39f034d7812d2420573218c69313ac31fd516ffebe1a57f4e41a32e1e840b9

b'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855  /tmp/tar_a0.tgz\n'
b'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855  /tmp/tar_a1.tgz\n'
b'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855  /tmp/gzp_a0.tgz\n'
b'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855  /tmp/gzp_a1.tgz\n'
```

As you can see the tar generated using the `tar` command are always same, instead the one generated using python are not.

Am I missing some arguments?

Thanks