hg: openjfx/jfx-dev/rt: 8200300: better gradle error message

[johan at lodgon.com]

Changeset: b9915cc91652
Author:    jvos
Date:      2018-04-14 11:00 +0200
URL:       http://hg.openjdk.java.net/openjfx/jfx-dev/rt/rev/b9915cc91652

8200300: better gradle error message
Reviewed-by: kcr, arapte
Contributed-by: abhinay.agarwal at gluonhq.com

! buildSrc/linux.gradle