IOException when output directory is missing

[allanrenucci]

> dotc -d out Foo.scala
java.io.IOException: No such file or directory
	at java.io.UnixFileSystem.createFileExclusively(Native Method)
	at java.io.File.createNewFile(File.java:1012)
	at dotty.tools.io.AbstractFile.fileOrSubdirectoryNamed(AbstractFile.scala:236)
	at dotty.tools.io.AbstractFile.fileNamed(AbstractFile.scala:247)
	at scala.tools.nsc.backend.jvm.BytecodeWriters.getFile(BytecodeWriters.scala:35)
	at scala.tools.nsc.backend.jvm.BCodeHelpers.getFileForClassfile(BCodeHelpers.scala:38)
	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.visit$$anonfun$1(GenBCode.scala:217)
	at scala.Option.foreach(Option.scala:257)
	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.visit(GenBCode.scala:219)
	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.run(GenBCode.scala:152)
	at dotty.tools.backend.jvm.GenBCodePipeline.buildAndSendToDisk(GenBCode.scala:367)
	at dotty.tools.backend.jvm.GenBCodePipeline.run(GenBCode.scala:333)
	at dotty.tools.backend.jvm.GenBCode.run(GenBCode.scala:54)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$2(Phases.scala:283)
	at scala.collection.immutable.List.map(List.scala:284)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:285)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1$$anonfun$1(Run.scala:81)
	at scala.compat.java8.JProcedure1.apply(JProcedure1.java:18)
	at scala.compat.java8.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
	at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:186)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:89)
	at scala.compat.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.util.Stats$.monitorHeartBeat(Stats.scala:76)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:94)
	at dotty.tools.dotc.Run.compileSources(Run.scala:63)
	at dotty.tools.dotc.Run.compile(Run.scala:47)
	at dotty.tools.dotc.Driver.doCompile(Driver.scala:26)
	at dotty.tools.dotc.Driver.process(Driver.scala:124)
	at dotty.tools.dotc.Driver.process(Driver.scala:93)
	at dotty.tools.dotc.Driver.process(Driver.scala:105)
	at dotty.tools.dotc.Driver.main(Driver.scala:132)
	at dotty.tools.dotc.Main.main(Main.scala)

dotc should emit a proper error message like scalac

> scalac -d out Foo.scala
scalac error: out does not exist or is not a directory
  scalac -help  gives more information