move the code to Addon#available?

src/lib/registration/addon.rb

@@ -65,7 +65,6 @@ def create_addon_with_deps(root)
     # delegate methods to underlaying suse connect object
     def_delegators :@pure_addon,
       :arch,
-      :available,
       :description,
       :eula_url,
       :free,
@@ -112,8 +111,7 @@ def selectable?
       # Do not support unregister
       return false if registered?
       # Do not select not available addons
-      # (explicitly check for false, it's reported only by SMT)
-      return false if available == false
+      return false if !available?
       # Do not allow to select child without selected or already registered parent
       return false if depends_on && !(depends_on.selected? || depends_on.registered?)
       # Do not allow to unselect parent if any children is selected
@@ -122,5 +120,14 @@ def selectable?
       return true
     end
 
+    # is the addon available? SMT may have mirrored only some extensions,
+    # the not mirrored extensions are marked as not available
+    # @return [Boolean] true if the addon is available to register
+    def available?
+      # explicitly check for false, undefined (nil) means it is available,
+      # it's only reported by SMT
+      @pure_addon.available != false
+    end
+
   end
 end

src/lib/registration/ui/addon_selection_dialog.rb

@@ -120,8 +120,7 @@ def addon_checkbox(addon, extra_spacing)
       def addon_checkbox_element(addon)
         # checkbox label for an unavailable extension
         # (%s is an extension name)
-        label = (addon.available == false) ? (_("%s (not available)") % addon.label) :
-          label.addon
+        label = addon.available? ? addon.label : (_("%s (not available)") % addon.label)
 
         CheckBox(Id(addon.identifier),
           Opt(:notify),