Intermittent failure in creating H2O cloud

Though I get a cloud eventually, it still does fail now and then.
So I'll make a habit out of reporting the stack traces, so you know it still has rough edges.

The incantation code:

from pysparkling import *
conf = (H2OConf(sc)
.use_auto_cluster_start()
.set_yarn_queue("spark-analytics")
.set_num_of_external_h2o_nodes(8)
.set_mapper_xmx("10G")
)

context = H2OContext.getOrCreate(sc, conf)

Many times this works, but today I got:

Py4JJavaError: An error occurred while calling z:org.apache.spark.h2o.JavaH2OContext.getOrCreate.
: java.io.FileNotFoundException: notify_sparkling-water-bteeuwen_155098482 (No such file or directory)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:146)
at scala.io.Source$.fromFile(Source.scala:91)
at scala.io.Source$.fromFile(Source.scala:76)
at scala.io.Source$.fromFile(Source.scala:54)
at org.apache.spark.h2o.backends.external.ExternalH2OBackend.launchH2OOnYarn(ExternalH2OBackend.scala:75)
at org.apache.spark.h2o.backends.external.ExternalH2OBackend.init(ExternalH2OBackend.scala:109)
at org.apache.spark.h2o.H2OContext.init(H2OContext.scala:102)
at org.apache.spark.h2o.H2OContext$.getOrCreate(H2OContext.scala:279)
at org.apache.spark.h2o.H2OContext.getOrCreate(H2OContext.scala)
at org.apache.spark.h2o.JavaH2OContext.getOrCreate(JavaH2OContext.java:195)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:237)
at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:357)
at py4j.Gateway.invoke(Gateway.java:280)
at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:132)
at py4j.commands.CallCommand.execute(CallCommand.java:79)
at py4j.GatewayConnection.run(GatewayConnection.java:214)
at java.lang.Thread.run(Thread.java:745)

I reran the code, and it worked.