Start using python{,3}-apt for sources.list handling.
generate_sources_list now operates in a pipeline-like model, where each
stage performs one specific transformation on the list of entries.
Restore noproxy to support the CI jobs.
Adding sitepackages means that lookup of commands gets weird, but using
{envpython} -m foo solves that.
So we need two {envpythons}, one for noproxy, one for nose.
We could stuff that into the noproxy script but that would be unexpected
for a script that only adjusts the environment then execs the real
command.
tests: update to demonstrate python-apt functional
Prior to pulling in python{,3}-apt functionality, show a simple set of
tests that demonstrate that it is functional in the test environments.
The noproxy script has been removed from tox.ini because we need to
set sitepackages=True to get python-apt, but doing so means we need to
find nose with 'python -m'. Also, it's safe to remove 'noproxy'
becuase the operation it was doing was a no-op for tox anyhow (those
proxy variables are not getting passed thru unless we set them
manually in tox.ini)
With noproxy unused by tox, it had no users, so remove it entirely.
