Python - dependencies - requirements.txt and setup.py

So none of us are particular python gurus.. we're all a buncha hacks..

We had project X which called out module Y and module Z in requirements.txt.
However... module Y also listed module Z in module Y's setup.py.
So we thought... we should remove module Z from project X's requirements.txt since it will be installed (by pip) as a transitive dependency when module Y was installed.

Then I read this post and decided we were wrong:

http://blog.miguelgrinberg.com/post/the-package-dependency-blues

Long story short:  when you are testing your app, its good to lock-down the versions you install and test against.  Thats what requirements.txt allowed us to do....specify a version for module Z.  Whereas if we allowed pip to decide the version of module Z by what was called out in Module Y's setup.py....that developer could end up with a newer version of the module Z which could include breaking changes.

*Module Y's setup.py had something like "module Z >= 1.0.0" and thus the upper version was not restricted.