Fix up 2to3 complaints. I've decided to do with wrapping list
comprehension inside list() to get the generators to run in several
places instead of list(map( or list(filter( which seem less readable to
me.
This allows us to create these objects without needing workdir,
which means we can use them outside of __init__.py.
We can also write them directly to their final destination
instead of writing them to the workdir and then copying them in.
