[2428] Put internal exception to anonymous namespace

src/lib/dns/master_loader.cc

@@ -31,6 +31,8 @@ using boost::algorithm::iequals;
 namespace isc {
 namespace dns {
 
+namespace {
+
 // An internal exception, used to control the code flow in case of errors.
 // It is thrown during the loading and caught later, not to be propagated
 // outside of the file.
@@ -41,6 +43,8 @@ public:
     {}
 };
 
+}
+
 class MasterLoader::MasterLoaderImpl {
 public:
     MasterLoaderImpl(const char* master_file,