Cryptographic verification for charmhelpers.fetch

[Matthew Wedgwood]

One of the features of the original charm-helpers shell library was cryptographic verification of downloaded files. A similar feature should be added to charmhelpers.fetch.

[Nathan Osman (george-edison55)]

This appears to be implemented: https://pythonhosted.org/charmhelpers/api/charmhelpers.fetch.html#charmhelpers.fetch.install_remote

The example provided demonstrates SHA-1 verification:

    dest = install_remote('http://example.com/archive.tgz',
          checksum='deadbeef',
          hash_type='sha1')