- refactor: return string instead of object

bin/slubsipbuilderbagit.pl

@@ -204,7 +204,7 @@ package SLUB::LZA::SIPBuilderBagIt;
                 SLUB::LZA::SIPBuilderBagIt::write_file("DEBUG_${ppn}_marc.xml", $marcblob_patched);
             }
 
-            return $marcblob_patched;
+            return $marcblob_patched->toString();
         }
         else {
             carp("Problem asking catalogue at $url using $ppn");