user_options = []

def initialize_options(self):
    pass

def finalize_options(self):
    pass

def run(self):
    pass


class build(_build):
    sub_commands = _build.sub_commands + [('build_css', None)]
setuptools.setup(cmdclass={'bdist_egg': bdist_egg, 'build': build,
    'build_css': build_css})
Запуск пользовательской сборки setuptools во время установки