fix rollup warning for this

Author: rmorshea

tests/js/rollup.config.js

@@ -19,4 +19,15 @@ export default {
       ),
     }),
   ],
+  onwarn: function (warning) {
+    // Skip certain warnings
+
+    // should intercept ... but doesn't in some rollup versions
+    if (warning.code === "THIS_IS_UNDEFINED") {
+      return;
+    }
+
+    // console.warn everything else
+    console.warn(warning.message);
+  },
 };