Snapcraft version string doesn't allow certain characters

[Alan Pope 🍺🐧🐱 🦄]

version: '2018_931-01'

"Issues while validating None: The 'version' property does not match the required schema: '2018_931-01' is not a valid snap version. Snap versions consist of upper- and lower-case alphanumeric characters, as well as periods, colons, plus signs, tildes, and hyphens. They cannot begin with a period, colon, plus sign, tilde, or hyphen. They cannot end with a period, colon, or hyphen.
"

The output of 'snapcraft init' says:-

version: '0.1' # just for humans, typically '1.2+git' or '1.3.2'

If it's "Just for humans" then maybe we shouldn't prescribe what version number the upstream developer should use, in their already established version system?

[John Lenton (chipaca)]

if this is indeed a bug, note you'll need bug tasks on snapd, review-tools, and snapstore as well as here.