How to fix: "RuntimeWarning: Model  was already registered."
Exactly the same problem had happened to me. The problem was that I had defined a model twice! Removing one of them solved the problem.
Since upgrading Django, I've been getting this error in iPython when I do imports:

RuntimeWarning: Model 'docket.search' was already registered. Reloading models is not advised as it can lead to inconsistencies, most notably with related models.

I'm guessing this is some automatic feature of iPython, but is there an easy solution? Is this something I even need to solve?