If a setup.py file exists it ought to have something in it before we
consider the source tree to be a Python module and treating it as such.
(A counter-example is https://www.bro.org/downloads/binpac-0.50.tar.gz -
it's not clear why this has a zero-length setup.py in it but we should
pay no attention to it.)
Fixes [YOCTO #12923].
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
