Operation.toString() throws IllegalStateException if there are unset key columns

Hi,

When trying java kudu api in spark-shell. I met error when tried to insert data into kudu.

In spark-shell:

scala> import org.apache.kudu.ColumnSchema;
import org.apache.kudu.ColumnSchema

scala> import org.apache.kudu.Schema;
import org.apache.kudu.Schema

scala> import org.apache.kudu.Type;
import org.apache.kudu.Type

scala> import org.apache.kudu.client._
import org.apache.kudu.client._

scala> import java.util.ArrayList;
import java.util.ArrayList

scala> import java.util.List;
import java.util.List

scala> val kc = new KuduClient.KuduClientBuilder("XXX.XXX.XXX.XXX:7051").build()
kc: org.apache.kudu.client.KuduClient = org.apache.kudu.client.KuduClient@2b852e9

scala> val ktbl = kc.openTable("kudu_scala_test")
ktbl: org.apache.kudu.client.KuduTable = org.apache.kudu.client.KuduTable@7e26fb98

scala> val ksession = kc.newSession()
ksession: org.apache.kudu.client.KuduSession = org.apache.kudu.client.KuduSession@cc1f71e

scala> val kins = ktbl.newInsert()
java.lang.IllegalStateException: Column id is not set <== id is the first column in the table.
at org.apache.kudu.client.shaded.com.google.common.base.Preconditions.checkState(Preconditions.java:197)
at org.apache.kudu.client.PartialRow.appendDebugString(PartialRow.java:559)
at org.apache.kudu.client.PartialRow.stringifyRowKey(PartialRow.java:532)
at org.apache.kudu.client.Operation.toString(Operation.java:202)
at scala.runtime.ScalaRunTime$.scala$runtime$ScalaRunTime$$inner$1(ScalaRunTime.scala:324)
at scala.runtime.ScalaRunTime$.stringOf(ScalaRunTime.scala:329)
at scala.runtime.ScalaRunTime$.replStringOf(ScalaRunTime.scala:337)
at .<init>(<console>:10)
at .<clinit>(<console>)
at $print(<console>)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.spark.repl.SparkIMain$ReadEvalPrint.call(SparkIMain.scala:1045)
at org.apache.spark.repl.SparkIMain$Request.loadAndRun(SparkIMain.scala:1326)
at org.apache.spark.repl.SparkIMain.loadAndRunReq$1(SparkIMain.scala:821)
at org.apache.spark.repl.SparkIMain.interpret(SparkIMain.scala:852)
at org.apache.spark.repl.SparkIMain.interpret(SparkIMain.scala:800)
at org.apache.spark.repl.SparkILoop.reallyInterpret$1(SparkILoop.scala:857)
at org.apache.spark.repl.SparkILoop.interpretStartingWith(SparkILoop.scala:902)
at org.apache.spark.repl.SparkILoop.command(SparkILoop.scala:814)
at org.apache.spark.repl.SparkILoop.processLine$1(SparkILoop.scala:657)
at org.apache.spark.repl.SparkILoop.innerLoop$1(SparkILoop.scala:665)
at org.apache.spark.repl.SparkILoop.org$apache$spark$repl$SparkILoop$$loop(SparkILoop.scala:670)
at org.apache.spark.repl.SparkILoop$$anonfun$org$apache$spark$repl$SparkILoop$$process$1.apply$mcZ$sp(SparkILoop.scala:997)
at org.apache.spark.repl.SparkILoop$$anonfun$org$apache$spark$repl$SparkILoop$$process$1.apply(SparkILoop.scala:945)
at org.apache.spark.repl.SparkILoop$$anonfun$org$apache$spark$repl$SparkILoop$$process$1.apply(SparkILoop.scala:945)
at scala.tools.nsc.util.ScalaClassLoader$.savingContextLoader(ScalaClassLoader.scala:135)
at org.apache.spark.repl.SparkILoop.org$apache$spark$repl$SparkILoop$$process(SparkILoop.scala:945)
at org.apache.spark.repl.SparkILoop.process(SparkILoop.scala:1064)
at org.apache.spark.repl.Main$.main(Main.scala:31)
at org.apache.spark.repl.Main.main(Main.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:731)
at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:181)
at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:206)
at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:121)
at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)

I have tried the kudu java sample, it worked well in java.