W0529 23:49:19.006525 22471 pailgun_service.py:69] encountered exception during SchedulerService.get_build_graph():
                     Traceback (most recent call last):
                     File "/home/travis/build/pantsbuild/pants/src/python/pants/pantsd/service/pailgun_service.py", line 65, in runner_factory
                     build_graph = self._scheduler_service.get_build_graph(spec_roots)
                     File "/home/travis/build/pantsbuild/pants/src/python/pants/pantsd/service/scheduler_service.py", line 84, in get_build_graph
                     return self._graph_helper.create_graph(spec_roots)
                     File "/home/travis/build/pantsbuild/pants/src/python/pants/bin/engine_initializer.py", line 64, in create_graph
                     for _ in graph.inject_specs_closure(spec_roots):  # Ensure the entire generator is unrolled.
                     File "/home/travis/build/pantsbuild/pants/src/python/pants/engine/legacy/graph.py", line 169, in inject_specs_closure
                     for address in self._inject(specs):
                     File "/home/travis/build/pantsbuild/pants/src/python/pants/engine/legacy/graph.py", line 185, in _inject
                     entries = maybe_list(state.value, expected_type=LegacyTarget)
                     AttributeError: 'NoneType' object has no attribute ‘value’