I had to do this additional step to allow the user to log-in again.
(I did not build the docs and I am not a rst person, but I think the change should be valid rst.)
Removes a lot of 'sudo -E' usage, and eventually should
let us get rid of the $PATH override for jupyterhub-admins,
which arguably is less secure than just dropping stuff into
/usr/bin
Also remove sudo -E from apt and mkdir calls. Not necessary.
