It seems impossible to run snap_1 from snap_2 where snap_2 is classic. This seems significant.
alan@hal:~$ snap version snap 220.127.116.11 snapd 18.104.22.168 series 16 ubuntu 16.04 kernel 4.10.0-41-generic
alan@hal:~$ snap run zzt cannot execute snap-update-ns: Permission denied snap-update-ns failed with code 1: No such file or directory
Steps to reproduce.
snap install cool-retro-term --classic snap install zzt snap run cool-retro-term
Then, inside cool-retro-term (which, is very cool).
snap run zzt
Here’s a pretty picture.