find_package() doesn't find 3.3-style no-__init__.py packages
setup(... packages=find_packages(..) )
on the developer machine will fail to find packages that lack a
__init__.py file, as is allowed in Python 3.3. However, such packages listed explicitly: packages=['mypkg'] do appear to get included and later installed.
Note: When testing this, before each test be sure to delete all generated metadata, including that which setup may previously have placed in the original source directory, as it seems that setup may use metadata created on a previous run in order to include files.
This is part of a general problem reported in issue #83, but I've logged it separately as it's specifically about setuptools.