E           Computing Task(create_pex_from_target_closure(), (<pants.backend.python.subsystems.python_native_code.PythonNativeCode object at 0x1063a2e10>+<pants.backend.python.subsystems.python_setup.PythonSetup object at 0x1063a2da0>+<pants.backend.python.subsystems.subprocess_environment.SubprocessEnvironment object at 0x1063a2eb8>+<pants.source.source_root.SourceRootConfig object at 0x1083254a8>+CreatePexFromTargetClosure(addresses=<pants.engine.addressable.Addresses object at 0x108325588>, output_filename='hello_world.pex', entry_point=None)), Pex, true)
                     E             Computing Task(transitive_hydrated_targets(), <pants.engine.addressable.Addresses object at 0x108325588>, TransitiveHydratedTargets, true)
                     E               Computing Task(transitive_hydrated_target(), foo/bar/hello_world:hello_world, TransitiveHydratedTarget, true)
                     E                 Computing Task(hydrate_target(), foo/bar/hello_world:hello_world, HydratedTarget, true)
                     E                   Computing Task(hydrate_struct(), foo/bar/hello_world:hello_world, HydratedStruct, true)
                     E                     Computing Task(parse_address_family(), Dir(path='foo/bar/hello_world'), AddressFamily, true)
                     E                       Throw(Directory "foo/bar/hello_world" does not contain any BUILD files.)
                     E                         Traceback (most recent call last):
                     E                           File "/Users/benjyw/src/pants/.pants.d/pyprep/sources/332bd781b5094207bbfda46605ed39fed8d66b78/pants/engine/native.py", line 485, in extern_generator_send
                     E                             res = c.from_value(func[0]).send(c.from_value(arg[0]))
                     E                           File "/Users/benjyw/src/pants/.pants.d/pyprep/sources/332bd781b5094207bbfda46605ed39fed8d66b78/pants/engine/build_files.py", line 53, in parse_address_family
                     E                             'Directory "{}" does not contain any BUILD files.'.format(directory.path)
                     E                         pants.engine.mapper.ResolveError: Directory "foo/bar/hello_world" does not contain any BUILD files.