If I run the test on Python 2, I don't get the error, and on line 93, brdicts is a dict.
However, if I run the test on Python 3, brdicts is a Deferred, thus the error.
This really ought to be impossible. If I were seeing this, single-stepping through inlineCallbacks in pudb would probably be my next step. Have you made any attempts to simplify it down to remove some of the buildbot-specific code?