bazaar.launchpad links have inconsistent checksums

[Robin H. Johnson]

Tarballs of bzr revisions, such as those available at http://bazaar.launchpad.net/~cloud-init-dev/cloud-init/trunk/tarball/1212 have inconsistent checksums, because the gzip header contains the compression timestamp, which changes.

This means that externally they cannot be relied on to have verified content.

Example of problem:

$ wget http://bazaar.launchpad.net/~cloud-init-dev/cloud-init/trunk/tarball/1212 -O a
$ sleep 5
$ wget http://bazaar.launchpad.net/~cloud-init-dev/cloud-init/trunk/tarball/1212 -O b
$ sha256sum a b
83a34a4177638a8b1aa92efd8f66fdc927c46f83021d8cf3d969783eaa2a8bd8 a
255199258e761732accaf3d0c3981a91c35289bce8f7aacaa9f967d2e5e1f14d b
$ file a b
a: gzip compressed data, last modified: Thu Apr 28 17:16:17 2016, max compression
b: gzip compressed data, last modified: Thu Apr 28 17:16:22 2016, max compression

Please exclude the timestamp from the tarballs, to ensure that the checksum is consistent.