Add helpful comments to unit test.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Add a RawFile object.

This provides support for storing raw data under the transactions
infrastructure.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Avoid using print().

The print() notation makes syntax checkers go crazy for some reason (notably
when Syntastic tries to validate Python 3 code with /usr/bin/python), so
switch to a syntax that is slightly more Python 2-friendly.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>