Revert to lab 0.34.12 and fix associated extensions

base-notebook/Dockerfile

@@ -93,9 +93,9 @@ RUN conda install --quiet --yes 'tini=0.18.0' && \
 RUN conda install --quiet --yes \
     'notebook=5.7.0' \
     'jupyterhub=0.9.4' \
-    'jupyterlab=0.35.2' && \
+    'jupyterlab=0.34.12' && \
     conda clean -tipsy && \
-    jupyter labextension install @jupyterlab/hub-extension@^0.12.0 && \
+    jupyter labextension install @jupyterlab/hub-extension@^0.11.0 && \
     npm cache clean --force && \
     jupyter notebook --generate-config && \
     rm -rf $CONDA_DIR/share/jupyter/lab/staging && \

scipy-notebook/Dockerfile

@@ -50,7 +50,7 @@ RUN conda install --quiet --yes \
     # Also activate ipywidgets extension for JupyterLab
     # Check this URL for most recent compatibilities
     # https://github.com/jupyter-widgets/ipywidgets/tree/master/packages/jupyterlab-manager
-    jupyter labextension install @jupyter-widgets/jupyterlab-manager@^0.38.0 && \
+    jupyter labextension install @jupyter-widgets/jupyterlab-manager@^0.37.0 && \
     # Pin to 0.6.2 until we can move to Lab 0.35 (jupyterlab_bokeh didn't bump to 0.7.0)
     jupyter labextension install jupyterlab_bokeh@0.6.2 && \
     npm cache clean --force && \