Pass environment variables through ssh

I deployed `batchspawner` again on Comet with a deployment quite similar to my old setup: https://github.com/jupyterhub/jupyterhub-deploy-hpc/tree/master/batchspawner-xsedeoauth-sshtunnel-sdsccomet
Here I ssh into a Comet login node to submit jobs, therefore I need to have the JupyterHub environment variables passed through the SSH session so that it is then passed into the SLURM job.
I am not sure how this could have worked in my old deployment, so it is possible I am missing something.
In my newer deployment I have to explicitely call `ssh` passing all the variables, see:
https://gist.github.com/zonca/55f7949983e56088186e99db53548ded#file-spawner-py-L42

Everything works fine, but there must be a better way, any suggestions?

I'll contribute this as another example for https://github.com/jupyterhub/jupyterhub-deploy-hpc