Allow passout home to be given via the environment.
Rejiggle some variable naming.
Remove dependency upon $HOME.

Do not reply upon setting $HOME to trick gpg and passout into using the test
dir for storage. This means python will see modules in ~/.local (e.g.
pdbpp) once again.
OOify tests.

Reduces the number of imports needed all over the place.
PEP8
Tidy imports.
Use a fresh GPG key for every test.