CI failures

[jrbourbeau]

There are a few test failures on master that I came across in #33 and thought it was worth opening up a separate issue.

The test failures are due to a ChildProcessError. For example, the traceback for pytest dask_xgboost/tests/test_core.py::test_classifier on master is

Traceback details

[gw0] darwin -- Python 3.6.6 /Users/jbourbeau/miniconda/envs/quansight/bin/python
loop = <tornado.platform.asyncio.AsyncIOLoop object at 0x1c1a8e8080>

    def test_classifier(loop):  # noqa
>       with cluster() as (s, [a, b]):

dask_xgboost/tests/test_core.py:38:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
../../miniconda/envs/quansight/lib/python3.6/contextlib.py:81: in __enter__
    return next(self.gen)
../../miniconda/envs/quansight/lib/python3.6/site-packages/distributed/utils_test.py:626: in cluster
    scheduler_q = mp_context.Queue()
../../miniconda/envs/quansight/lib/python3.6/multiprocessing/context.py:102: in Queue
    return Queue(maxsize, ctx=self.get_context())
../../miniconda/envs/quansight/lib/python3.6/multiprocessing/queues.py:42: in __init__
    self._rlock = ctx.Lock()
../../miniconda/envs/quansight/lib/python3.6/multiprocessing/context.py:67: in Lock
    return Lock(ctx=self.get_context())
../../miniconda/envs/quansight/lib/python3.6/multiprocessing/synchronize.py:163: in __init__
    SemLock.__init__(self, SEMAPHORE, 1, 1, ctx=ctx)
../../miniconda/envs/quansight/lib/python3.6/multiprocessing/synchronize.py:81: in __init__
    register(self._semlock.name)
../../miniconda/envs/quansight/lib/python3.6/multiprocessing/semaphore_tracker.py:83: in register
    self._send('REGISTER', name)
../../miniconda/envs/quansight/lib/python3.6/multiprocessing/semaphore_tracker.py:90: in _send
    self.ensure_running()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <multiprocessing.semaphore_tracker.SemaphoreTracker object at 0xa16135320>

    def ensure_running(self):
        '''Make sure that semaphore tracker process is running.

        This can be run from any process.  Usually a child process will use
        the semaphore created by its parent.'''
        with self._lock:
            if self._pid is not None:
                # semaphore tracker was launched before, is it still running?
>               pid, status = os.waitpid(self._pid, os.WNOHANG)
E               ChildProcessError: [Errno 10] No child processes

../../miniconda/envs/quansight/lib/python3.6/multiprocessing/semaphore_tracker.py:46: ChildProcessError

[mrocklin]

Unfortunately I don't have much insight to share here. This probably requires some investigation.

[quartox]

@TomAugspurger commented in #31 that it has something to do with a new xgboost update making it incompatible.