Assertion facet->is_ghost() failed for DG problem in parallel

I am running FEniCS master. This script

from dolfin import *                                                                                                                                                                                                  
mesh = UnitSquareMesh(10, 10)                                                                                                                                                                                               
Z = FunctionSpace(mesh, "DG", 1)
u = TrialFunction(Z)
v = TestFunction(Z)                                                                                                                                                                                               
F1 = u('-')*v('-')*dS  
assemble(F1)

fails with the following error message when running in parallel:

simon@doodson ~git:master$ mpirun -n 2 python test.py 
subprocess32 module not found! Using unsafe built-insubprocess module instead. Install subprocess32 for thread-safety and safe usage on OFED/Infiniband networks.
subprocess32 module not found! Using unsafe built-insubprocess module instead. Install subprocess32 for thread-safety and safe usage on OFED/Infiniband networks.
Traceback (most recent call last):
  File "test.py", line 10, in <module>
    assemble(F1)
  File "/home/simon/src/fenics_master/dolfin/local.master/lib/python2.7/site-packages/dolfin/fem/assembling.py", line 203, in assemble
Traceback (most recent call last):
  File "test.py", line 10, in <module>
    assemble(F1)
  File "/home/simon/src/fenics_master/dolfin/local.master/lib/python2.7/site-packages/dolfin/fem/assembling.py", line 203, in assemble
    assembler.assemble(tensor, dolfin_form)
RuntimeError:     assembler.assemble(tensor, dolfin_form)
RuntimeError: 

*** -------------------------------------------------------------------------
*** DOLFIN encountered an error. If you are not able to resolve this issue
*** using the information listed below, you can ask for help at
***
***     fenics-support@googlegroups.com
***
*** Remember to include the error message listed below and, if possible,
*** include a *minimal* running example to reproduce the error.
***
*** -------------------------------------------------------------------------
*** Error:   Unable to complete call to function build().
*** Reason:  Assertion facet->is_ghost() failed.
*** Where:   This error was encountered inside /home/simon/src/fenics_master/dolfin_master/dolfin/fem/SparsityPatternBuilder.cpp (line 202).
*** Process: 0
*** 
*** DOLFIN version: 2016.2.0.dev0
*** Git changeset:  8622ca77d212622ae82cea8325ed22ad26d3cd5d
*** -------------------------------------------------------------------------


*** -------------------------------------------------------------------------
*** DOLFIN encountered an error. If you are not able to resolve this issue
*** using the information listed below, you can ask for help at
***
***     fenics-support@googlegroups.com
***
*** Remember to include the error message listed below and, if possible,
*** include a *minimal* running example to reproduce the error.
***
*** -------------------------------------------------------------------------
*** Error:   Unable to complete call to function build().
*** Reason:  Assertion facet->is_ghost() failed.
*** Where:   This error was encountered inside /home/simon/src/fenics_master/dolfin_master/dolfin/fem/SparsityPatternBuilder.cpp (line 202).
*** Process: 1
*** 
*** DOLFIN version: 2016.2.0.dev0
*** Git changeset:  8622ca77d212622ae82cea8325ed22ad26d3cd5d
*** -------------------------------------------------------------------------


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mpirun noticed that process rank 1 with PID 20238 on node doodson exited on signal 6 (Aborted).
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