Correctly set PYTHONPATH for module test. (#1240)
Correctly set PYTHONPATH for module test. (#1240)

PYTHONPATH should be prepended if set or else the test hangs if
distributed is in a non-standard path.
dask/distributed,dask/distributed,mrocklin/distributed,blaze/distributed,blaze/distributed,mrocklin/distributed,dask/distributed,dask/distributed,mrocklin/distributed