Check dask-labextension is available

[GenevieveBuckley]

What happened:
I created a tutorial environment using the conda instructions in the README. It said everything had installed correctly into my conda environment, including the dask labextension. But when I started jupyter lab, the dask labextension was not available in the left hand sidebar.

What you expected to happen:
I expected the dask labextension to be available to me when I started running jupyter lab.

Minimal Complete Verifiable Example:

git clone http://github.com/dask/dask-tutorial
cd dask-tutorial

conda env create -f binder/environment.yml
conda activate dask-tutorial
jupyter labextension install @jupyter-widgets/jupyterlab-manager
jupyter labextension install @bokeh/jupyter_bokeh

jupyter lab

The jupyter lab extension icon is not visible to me in the left hand sidebar.

Anything else we need to know?:
Reinstalling the dask-labextension with pip fixed the problem.

conda uninstall --force dask-labextension
python -m pip install dask-labextension

Environment:

• Dask version: 2021.8.0
• Python version: 3.8.12
• Operating System: Ubuntu 20.04 LTS
• Install method (conda, pip, source): conda

[jrbourbeau]

Thanks for surfacing this @GenevieveBuckley -- apologies for the delayed reply. It looks like the README is missing this extra installation step

dask-tutorial/binder/postBuild

Line 4 in d9193da

jupyter labextension install dask-labextension

FWIW once we migrate to JupyterLab 3, all those extra jupyter labextension install ... commands won't be needed anymore (xref #207)