Make extension shim handlers more robust.
Make extension shim handlers more robust.

It wasn’t matching request(‘jupyter-js-widgets’).
jupyter/jupyterlab,TypeFox/jupyterlab,jupyter/jupyterlab,eskirk/jupyterlab,TypeFox/jupyterlab,TypeFox/jupyterlab,charnpreetsingh185/jupyterlab,TypeFox/jupyterlab,charnpreetsingh185/jupyterlab,TypeFox/jupyterlab,charnpreetsingh185/jupyterlab,jupyter/jupyterlab,jupyter/jupyterlab,eskirk/jupyterlab,charnpreetsingh185/jupyterlab,eskirk/jupyterlab,charnpreetsingh185/jupyterlab,jupyter/jupyterlab,eskirk/jupyterlab,eskirk/jupyterlab