raising ArgumentError for circular dependency and self-linked contain…

…ers rather than RuntimeError

app/models/service_sorter.rb

@@ -23,9 +23,9 @@ def sort(services)
         def visit(n)
           if @temporary_marked.include?(n[:name])
             if get_service_names_for(n[:links]).include?(n[:name])
-              raise "An image can not link to itself: #{n[:name]}"
+              raise ArgumentError, "An image can not link to itself: #{n[:name]}"
             else
-              raise "Circular import between #{n[:name]} and #{@temporary_marked}"
+              raise ArgumentError, "Circular import between #{n[:name]} and #{@temporary_marked}"
             end
           end
 

spec/models/service_sorter_spec.rb

@@ -47,7 +47,7 @@
       end
 
       it 'raises an exception' do
-        expect{ described_class.sort(services) }.to raise_error(RuntimeError, /image can not link to itself/)
+        expect{ described_class.sort(services) }.to raise_error(ArgumentError, /image can not link to itself/)
       end
 
     end
@@ -61,7 +61,7 @@
       end
 
       it 'raises an exception' do
-        expect{ described_class.sort(services) }.to raise_error(RuntimeError, /Circular import/)
+        expect{ described_class.sort(services) }.to raise_error(ArgumentError, /Circular import/)
       end
 
     end