Attempting to install a snap that requires devmode without passing --devmode results in confusing error

[Chris Halse Rogers]

It appears that when a requesting to install a snap that requires devmode without passing --devmode that the snap does not exist, rather than that installing the snap requires passing --devmode.

For example:

> sudo snap install --beta ubuntu-image
[sudo] password for chris:
error: cannot install "ubuntu-image": snap not found
> sudo snap install --beta --devmode ubuntu-image
ubuntu-image (beta) 0.12+real1 from 'canonical' installed

I'd expect attempting to install ubuntu-image without passing --devmode would result in an error saying that the snap requires --devmode rather than an error saying the snap doesn't exist.

ProblemType: Bug
DistroRelease: Ubuntu 17.04
Package: snapd 2.18+17.04ubuntu3
ProcVersionSignature: Ubuntu 4.8.0+bcachefs.git.20161128.7bf9ed3-1-generic 4.8.1
Uname: Linux 4.8.0+bcachefs.git.20161128.7bf9ed3-1-generic x86_64
ApportVersion: 2.20.3-0ubuntu8
Architecture: amd64
CurrentDesktop: Unity
Date: Mon Dec 5 10:28:27 2016
SourcePackage: snapd
UpgradeStatus: No upgrade log present (probably fresh install)