title: scala Option mutually exclusive values
body: <p>I have an </p>
  
  <pre><code>val file: Option = xxxx
  val request: Option = yyyyy
  </code></pre>
  
  <p>These are mutually exclusive so naturally a for comprehension is what I want.  Is there a clean way of </p>
  
  <ol>
  <li>throwing validation exception if both are None</li>
  <li>throwing validation exception if both are Some(x)</li>
  <li>processing the one or the other</li>
  </ol>
  
  <p>I am thinking maybe match on a tuple may be the cleanest but wondering if there is some map or flatMap recoverWith/rescue trickery that might look readable and simple.</p>