show a nice msg when bind rpaas instance(already bind to an app) to another app

When we try to bind a rpaas instance that has already been binded to another one it shows me a msg and an error:

Error: Failed to bind the instance "rpaas-be-lab/teste" to the app "myapp2-static-galeb": <html>
  <head>
    <title>Internal Server Error</title>
  </head>
  <body>
    <h1>Internal Server Error</h1>

  </body>
</html>

This dont tell me that it has been binded to another app.
