title: Issues testing a media app in development mode
body: <p>For a couple of days recently, I was able to get my (prototype) media player app to show up as a menu item and run in the Android Auto app, in the Desktop Head Unit, and on my car. This is an app built and installed using Android Studio and run on a phone in developer mode with Android Auto in developer mode with the head unit server running. Older reports on StackOverflow say that uploading to Google Play is necessary to test an app in a real car, but I did not find this to be true.</p>
  
  <p>However, recently, it stopped working (on the Android Auto app and the car, have not tried DHU), and I do not understand what has changed. I suspect the issue might be related to signing my app, because it only started working when I started signing my app. The only clue I have are two cryptic messages in the log, which I also saw before I started signing the app.</p>
  
  <pre><code>I Finsky  : [25252] ude.dispatchTransaction(7): PlayGearheadService &lt;my.package.name&gt;, app owners empty
  W CAR.VALIDATOR: Package DENIED; failed all other checks [my.package.name] [CONTEXT service_id=13 ]
  </code></pre>