Fix JupyterHub version to 1.2.2 to prevent 500 (#58)
Fix JupyterHub version to 1.2.2 to prevent 500 (#58)

- With v1.3, render_template default to asyc which breaks the first login to Dataproc Hub.
- Although we can set a sync=True parameter in the GCP Proxy Authenticator, for now pinning JupyterHub version to 1.2.2 also fix the problem.
GoogleCloudDataproc/jupyterhub-dataprocspawner,GoogleCloudDataproc/jupyterhub-dataprocspawner,GoogleCloudDataproc/jupyterhub-dataprocspawner