Paper cuts

This is a minor release to fix a few issues in Snapcraft.

Sergio Schvezov

• ant plugin: correct default channel and improve help
• cli: improve help for push-metadata
• project, cli: clean up snap asset messages
• file utils: better error for NotADirectory
• cli: only say sorry for in-snapcraft issues

Chris Patterson

• deprecations: add deprecation notice for version-script (dn10)

Carlo Lobrano

• meta: add InvalidAppCommand errors for non-existent and not-found (#2539)