On an up to date xenial, installing the ubuntu-core snap which ships 2.25 makes all the snap commands fail with "internal error, please report: running "<invoked-command>" failed: no such file or directory":
ubuntu@autopkgtest:~$ snap list
Name Version Rev Developer Notes
ubuntu-core 16-2 2109 canonical -
ubuntu@autopkgtest:~$ snap changes
ID Status Spawn Ready Summary
1 Done 2017-05-08T15:27:08Z 2017-05-08T15:27:08Z Initialize system state
2 Done 2017-05-08T15:27:23Z 2017-05-08T15:28:29Z Install "ubuntu-core" snap from "beta" channel
ubuntu@autopkgtest:~$ snap version
snap 2.25
snapd 2.25
series 16
ubuntu 16.04
kernel 4.4.0-67-generic
ubuntu@autopkgtest:~$ sudo snap install test-snapd-tools
test-snapd-tools 1.0 from 'canonical' installed
ubuntu@autopkgtest:~$ /snap/bin/test-snapd-tools.echo hello!
internal error, please report: running "test-snapd-tools.echo" failed: no such file or directory
This is caused by current snapd code hardcoding "core" as the location of the snap that contains snap-confine and other internal tools.