tfx: BeamDagRunner, Transform deadlock with Python 3.6

Hi everyone,

Running the taxi_pipeline_beam example fails with

  from tensorflow_transform.output_wrapper import TFTransformOutput
  File "/srv/hops/anaconda/anaconda/envs/python36/lib/python3.6/site-packages/tensorflow_transform/output_wrapper.py", line 29, in <module>
    from tensorflow_transform.tf_metadata import metadata_io
  File "<frozen importlib._bootstrap>", line 968, in _find_and_load
  File "<frozen importlib._bootstrap>", line 149, in __enter__
  File "<frozen importlib._bootstrap>", line 94, in acquire
_frozen_importlib._DeadlockError: deadlock detected by _ModuleLock('tensorflow_transform.tf_metadata.metadata_io') at 139642620901192

while running Transform https://github.com/tensorflow/tfx/blob/0.14.0/tfx/examples/chicago_taxi_pipeline/taxi_pipeline_beam.py#L85

TFX version is 0.14, Beam is 2.15 and running on Flink 1.8.1.

All works well with Python 2.7. Has anyone encountered this issue before?

Thank you, Theo