Running the README example, I've seeing the following error:

File "/usr/local/spark-2.1.0-bin-hadoop2.7/python/lib/py4j-0.10.4-src.zip/py4j/java_gateway.py", line 1035, in send_command
    raise Py4JNetworkError("Answer from Java side is empty")
py4j.protocol.Py4JNetworkError: Answer from Java side is empty

Further investigation reveals that the java heap is being blown due to too-low memory settings on docker for mac. Linux won't see this issue so long as the memory available to the OS is sufficient to the task whereas docker for mac must explicitly allocate memory to a VM for containers to run