The custom bootstrapping to get a symbolic buildroot for

doc generation was affecting global state and leaving a

buildroot of <buildroot> laying around for subsequent code

to pick up and unwittingly try to use.
src/python/pants/backend/core/tasks/reflect.py | 13 ++++++++++++-

 1 file changed, 12 insertions(+), 1 deletion(-)

Locally this was failing before, passed after:
$ PANTS_DEV=1 ./pants goal test tests/python/pants_test/tasks:reflect tests/python/pants_test/backend/python:test_builder


Also generated docs and confirmed the intended symbolic <buildroot> was being interpolated: http://pantsbuild.github.io/jsirois/goals_reference.html#Common
Installed python 3.2.5 after which the following failed but then passed after diff 3:
$ PATH=/home/jsirois/.pyenv/versions/3.2.5/bin:$PATH pants.dev goal test tests/python/pants_test/tasks:reflect tests/python/pants_test/backend/python:test_builder


CI went green here: https://travis-ci.org/pantsbuild/pants/builds/43773742