Test flake: test_split_half_sdf

> raise RuntimeError(result.error)
E RuntimeError: Traceback (most recent call last):
E File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Python_Commit/src/sdks/python/test-suites/tox/py37/build/srcs/sdks/python/apache_beam/runners/worker/data_plane.py", line 487, in input_elements
E element = received.get(timeout=1)
E File "/usr/lib/python3.7/queue.py", line 178, in get
E raise Empty
E _queue.Empty
E
E During handling of the above exception, another exception occurred:
E
E Traceback (most recent call last):
E File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Python_Commit/src/sdks/python/test-suites/tox/py37/build/srcs/sdks/python/apache_beam/runners/worker/sdk_worker.py", line 267, in _execute
E response = task()
E File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Python_Commit/src/sdks/python/test-suites/tox/py37/build/srcs/sdks/python/apache_beam/runners/worker/sdk_worker.py", line 340, in <lambda>
E lambda: self.create_worker().do_instruction(request), request)
E File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Python_Commit/src/sdks/python/test-suites/tox/py37/build/srcs/sdks/python/apache_beam/runners/worker/sdk_worker.py", line 581, in do_instruction
E getattr(request, request_type), request.instruction_id)
E File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Python_Commit/src/sdks/python/test-suites/tox/py37/build/srcs/sdks/python/apache_beam/runners/worker/sdk_worker.py", line 618, in process_bundle
E bundle_processor.process_bundle(instruction_id))
E File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Python_Commit/src/sdks/python/test-suites/tox/py37/build/srcs/sdks/python/apache_beam/runners/worker/bundle_processor.py", line 985, in process_bundle
E expected_inputs):
E File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Python_Commit/src/sdks/python/test-suites/tox/py37/build/srcs/sdks/python/apache_beam/runners/worker/data_plane.py", line 490, in input_elements
E raise RuntimeError('Channel closed prematurely.')
E RuntimeError: Channel closed prematurely.