more

setup.py

@@ -28,8 +28,8 @@ def update_package_data(distribution):
 # The name of the project
 lab_path = (HERE / "nglview" / "staticlab")
 nb_path = (HERE / "nglview" / "static")
-assert (nb_path/"index.js").exists(), "index.js not found in %s" % nb_path
-assert (lab_path/"static/package.json").exists(), "package.json not found in %s" % lab_path
+assert (nb_path/"index.js").exists(), "index.js not found in %s. Make sure to build the frontend assets and install the JupyterLab extension." % nb_path
+assert (lab_path/"static/package.json").exists(), "package.json not found in %s. Make sure to build the frontend assets and install the JupyterLab extension." % lab_path
 labext_name = "nglview-js-widgets"
 package_data_spec = {
     labext_name: ["*"],