title: scala.io.Source.fromInputStream does not throw the MalformedInputException further
body: <p>I have the following scala code which takes a String, messes up with the UTF-8 characters and then tries to read it via Source.fromInputStream:  </p>
  
  <pre><code>import java.io.ByteArrayInputStream
  import java.nio.charset.StandardCharsets.UTF_8
  
  import scala.io.Source
  
  val stringSourceAsBytes = "hellö wörld".getBytes(UTF_8)
  
  val messedUpUTF8 = 128.toByte +: stringSourceAsBytes
  
  val linesIterator : Iterator[String] =
  try {
    val input = new ByteArrayInputStream(messedUpUTF8)
    Source.fromInputStream(input).getLines()
  }catch{
    case exc: Throwable =&gt; println(" This is an exception !")
    Iterator()
  }
  
  linesIterator.mkString("\n")
  </code></pre>
  
  <p>Shouldn't I see the "This is an exception !" message ? Because I don't see it. 
  Indeed I get a printed stack trace, but I cannot catch the exception and treat it properly ... </p>
  
  <p>BTW: my console shows: </p>
  
  <pre><code>java.nio.charset.MalformedInputException: Input length = 1
      at java.nio.charset.CoderResult.throwException(IO.sc:277)
     at sun.nio.cs.StreamDecoder.implRead(IO.sc:335)
     at sun.nio.cs.StreamDecoder.read(IO.sc:174)
     at java.io.InputStreamReader.read(IO.sc:181)
     at java.io.BufferedReader.fill(IO.sc:157)
     at java.io.BufferedReader.readLine(IO.sc:322)
     at java.io.BufferedReader.readLine(IO.sc:388)
     at scala.io.BufferedSource$BufferedLineIterator.hasNext(IO.sc:66)
     at scala.collection.Iterator.toString(IO.sc:1409)
     at scala.collection.Iterator.toString$(IO.sc:1409)
     at scala.collection.AbstractIterator.toString(IO.sc:1413)
     at #worksheet#.#worksheet#(IO.sc:53)
  </code></pre>