use VTK_ASSERT_MSG if a message is given

dune/vtk/vtkreader.impl.hh

@@ -599,7 +599,7 @@ std::map<std::string, std::string> VtkReader<Grid,Creator>::parseXml (std::strin
     case XML_NAME_ASSIGN:
       value.clear();
       escape = false;
-      VTK_ASSERT( c == '"' && "Format error!" );
+      VTK_ASSERT_MSG( c == '"', "Format error!" );
       sec = XML_VALUE;
       break;
     case XML_VALUE:
@@ -614,7 +614,7 @@ std::map<std::string, std::string> VtkReader<Grid,Creator>::parseXml (std::strin
       }
       break;
     default:
-      VTK_ASSERT(false && "Format error!");
+      VTK_ASSERT_MSG(false, "Format error!");
     }
   }