AVAudioSession - catching setMode and setCategory errors
<p>I'm using AVAudioSession in an app that only performs audio playback. I'm setting my audioSession's mode and category in <code>applicationDidFinishLaunchingWithOptions:</code>.</p>

<pre><code>let audioSession = AVAudioSession.sharedInstance()

do {
   try audioSession.setMode(AVAudioSessionModeDefault)
   try audioSession.setCategory(AVAudioSessionCategoryPlayback)
}
catch {}
</code></pre>

<p>I never set a different mode or category during my app's lifetime, and I activate my audio session when the user taps a play button. In what scenario would either of these methods (<code>setMode:error:</code> and <code>setCategory:error</code>) throw an error? What should I expect to handle in my catch block?</p>