[gnome-boxes/wip/rishi/rhel: 4/16] wizard-source: Use 'requires' instead of 'assert'

[Debarshi Ray <debarshir src gnome org>]

commit b96a1738a884458bb0531a38199f0af71dec0b4c
Author: Debarshi Ray <debarshir gnome org>
Date:   Wed Aug 23 18:44:26 2017 +0200

    wizard-source: Use 'requires' instead of 'assert'
    
    It seems nicer to use 'requires' (and 'ensures') for expressing post
    and pre-conditions. It is more readable and doesn't crash hard when an
    invariant is violated.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=786689

 src/wizard-source.vala |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/wizard-source.vala b/src/wizard-source.vala
index 70936a4..228720d 100644
--- a/src/wizard-source.vala
+++ b/src/wizard-source.vala
@@ -177,8 +177,8 @@ private class Boxes.WizardSource: Gtk.Stack {
         transition_type = Gtk.StackTransitionType.SLIDE_LEFT_RIGHT; // FIXME: Why this won't work from .ui 
file?
     }
 
-    public void setup_ui (AppWindow window) {
-        assert (window != null);
+    public void setup_ui (AppWindow window)
+        requires (window != null) {
 
         this.window = window;