Issue #3015199: Allow SkipOnValue to include a message in the MigrateSkipRowException.

Closes #3015199

src/Plugin/migrate/process/EntityValue.php

@@ -151,7 +151,7 @@ class EntityValue extends ProcessPluginBase implements ContainerFactoryPluginInt
       }
       else {
         if ($langcode) {
-          throw new \InvalidArgumentException('Langcode can only be used with content entities currently.');
+          throw new MigrateException('Langcode can only be used with content entities currently.');
         }
       }
       try {