title: Illegal 'sec-websocket-protocol' header: Invalid input 'EOI', expected sec-websocket-protocol
body: <p>I'm trying to connect on Kubernetes websocket API but I get this error message:</p>
  
  <pre><code>java.lang.IllegalStateException: Message failed with status code 400 Bad Request; Error info: ErrorInfo(Illegal 'sec-websocket-protocol' header: Invalid input 'EOI', expected sec-websocket-protocol (line 1, column 1),
  ^)
      at akka.http.impl.engine.ws.WebSocketClientBlueprint$UpgradeStage$1$$anon$1.onPush(WebSocketClientBlueprint.scala:107)
      at akka.stream.impl.fusing.GraphInterpreter.processPush(GraphInterpreter.scala:747)
      at akka.stream.impl.fusing.GraphInterpreter.execute(GraphInterpreter.scala:649)
      at akka.stream.impl.fusing.GraphInterpreterShell.runBatch(ActorGraphInterpreter.scala:471)
      at akka.stream.impl.fusing.GraphInterpreterShell.receive(ActorGraphInterpreter.scala:410)
      at akka.stream.impl.fusing.ActorGraphInterpreter.akka$stream$impl$fusing$ActorGraphInterpreter$$processEvent(ActorGraphInterpreter.scala:603)
      at akka.stream.impl.fusing.ActorGraphInterpreter$$anonfun$receive$1.applyOrElse(ActorGraphInterpreter.scala:618)
      at akka.actor.Actor.aroundReceive(Actor.scala:502)
      at akka.actor.Actor.aroundReceive$(Actor.scala:500)
      at akka.stream.impl.fusing.ActorGraphInterpreter.aroundReceive(ActorGraphInterpreter.scala:529)
      at akka.actor.ActorCell.receiveMessage(ActorCell.scala:526)
      at akka.actor.ActorCell.invoke(ActorCell.scala:495)
      at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:257)
      at akka.dispatch.Mailbox.run(Mailbox.scala:224)
      at akka.dispatch.Mailbox.exec(Mailbox.scala:234)
      at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
      at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
      at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
      at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
  </code></pre>
  
  <p>I must be missing some configuration, do you knwo where this comes from?</p>
  
  <p>Cheers</p>