fixes #3382

app/controllers/sources_controller.rb

@@ -1,5 +1,6 @@
 class SourcesController < ApplicationController
   respond_to :json, :xml
+  rescue_from Sources::Site::NoStrategyError, :with => :no_strategy
 
   def show
     @source = Sources::Site.new(params[:url], :referer_url => params[:ref])
@@ -9,4 +10,10 @@ class SourcesController < ApplicationController
       format.xml { render xml: @source.to_h.to_xml(root: "source") }
     end
   end
+
+protected
+
+  def no_strategy
+    render json: {message: "Unsupported site"}.to_json, status: 400
+  end
 end