Review Board had some code that optimized test run times by

pre-compiling any referenced fixtures and storing the results in a way

that could be quickly reused across tests. This cut down test time

considerably.
That code has been pulled out into a FixturesCompilerMixin, which any

test suite can use to get the same speed benefits.

Switched Review Board over to this, and saw that all unit tests passed.
Tested on another project, and saw that it also worked.