Install jupyterlab and jupyter_packaging in 1 cmd on CI

Author: jtpio

.github/workflows/build.yml

@@ -74,12 +74,14 @@ jobs:
         pip uninstall -y jupyter_widget_testwidgets
         cd jupyter-widget-testwidgets
         pip install .
-        jupyter nbextension enable --py --sys-prefix jupyter_widget_testwidgets
+
         # Validate nbextension (enable does not use exit code):
+        jupyter nbextension enable --py --sys-prefix jupyter_widget_testwidgets
         python -c "from notebook.nbextensions import validate_nbextension; import sys; sys.exit(validate_nbextension('jupyter_widget_testwidgets/extension') or 0)"
-        pip install jupyterlab
+
+        # Validate labextension
+        pip install -U jupyterlab~=3.0 jupyter_packaging~=0.7
         # Make sure our lab extension was installed.
         jupyter labextension list 2>&1 | grep -ie "jupyter-widget-testwidgets.*OK"
         # Make sure our lab extension can be develop installed.
-        pip install jupyter_packaging==0.7.9
         jupyter labextension develop . --overwrite