The oasa dependency is python, but it's not in the python package index.
I can install it manually by doing
$ pip install http://bkchem.zirael.org/download/oasa-0.13.1.tar.gz

What's the best way to declare this as a dependency?
I feel that
depends_on 'oasa' => :python
won't work as it's not in the python package index.
But that creating a brew formula for it will be discouraged because it's a python project.
Suggestions?

You can't depend on Python packages like that in Homebrew. You shouldn't build any bindings for the first version, we could add them later once we sort out some of the bindings issues. I'm not the expert on that, you'd probably have to ask adamv or mxcl.

I'm doing work in my deps branch to enable more complex external dependency scenarios, such as the oasa dep declared here.

I think this should be closed or talked about more.

I'll have to rebase my "improved dep support" on top of the other recent changes

Added as b10d691 - sorry about the delay.