Thanks Aymeric Augustin for shepherding the DEP and patch review.
Thanks Marten Kenbeek and Tim Graham for contributing to the code.
Thanks Tom Christie, Shai Berger, and Tim Graham for the docs.
Debian packages unconditionally byte-compile .py files on installation and
do not silence errors by design. Therefore, we need a way of shipping these
invalid .py files without a .py extension but ensuring that when we
template them, they end up as .py.
We don't special-case .py files so that the all the TemplateCommand
command-line options (eg. extra_files and extensions) still work entirely
as expected and it may even be useful for other formats too.