Bad error message when other app running on same port

[pedro rijo]

While migrating an existing app to Play2.5.8, I had another forgotten app running on port 9000 (too many desktops).

When I type sbt run I get

$ sbt run

[info] Loading project definition from XXX

[info] Set current project to XXX (in build file:/XXX)

--- (Running the application, auto-reloading is enabled) ---

[error] p.c.s.NettyServer - Failed to listen for HTTP on /0.0.0.0:9000!

[error] (compile:run) play.runsupport.ServerStartException

[error] Total time: 2 s, completed Sep 24, 2016 5:37:59 PM

After much time trying to figure out if I was missing some step on route generator, app loader or something else, when I was almost quitting for today, I saw I had other app running on the same port. As soon as I killed it, I was able to run the app. After a while I found someone else on SO with the same problem: http://stackoverflow.com/questions/36407305/nettyserver-not-started-for-play2-in-intellij

Why is play framework giving this generic and awful error message? I'm almost sure I already saw play logging an error message saying the port was already in use (probably in play 2.4.3/6)