[Distutils] Including tests in source package

[Stanisław Pitucha]

Hi all,
I'm trying to package tests file in the sdist only and it doesn't really
work :/
If I do:

setup(
   packages = find_packages(exclude=['tests']),
   test_suite = "tests",
   ...

this doesn't package tests anywhere. Using either general find_packages
includes tests in both sdist and bdist.
How can I resolve this? Essentially I want either tests.py, or
tests/__init__.py to be distributed in sdist, but not in bdist.

Thanks,
Stan