Error for Warning if setup.py does not have shebang

Despite the fact that python 3 documentation specify to use a shebang at setup.py:

from distutils.core import setup

setup(name='Distutils
    ...
)

https://docs.python.org/3.1/distutils/setupscript.html

Some projects does not have a shebang, like openstack nova:

https://github.com/openstack/nova/blob/master/setup.py

This patch relax the fact of exit with error if no shebang is provided

Signed-off-by: VictorRodriguez vm.rod25@gmail.com