setup.py : disable autodiscovery with later setuptools

Disable the autodiscovery [1] for this project; it looks like this is
used basically via it's tox environments and doesn't need to worry
about what packages it creates.

This is hitting now because the translation proposal jobs run under a
3.8 venv which is bringing in newer setuptools.

[1] https://github.com/pypa/setuptools/issues/3197

Change-Id: I1f833f6db5fe14f17c91aa2e1f132c2f0fa62959

setup.py

@@ -26,4 +26,5 @@ except ImportError:
 
 setuptools.setup(
     setup_requires=['pbr>=2.0.0'],
-    pbr=True)
+    pbr=True,
+    py_modules=[])