Check that resource names are valid

[cjwatson]

Checklist

• Confirmed this is an issue with charm-tools, not charmstore-client
• Provide versions of tools used
• Described the feature or ways to replicate the issue

What version am I running?

I ran the following command: charm version and got the following ouput:

charm 2.2.0-0ubuntu1~ubuntu16.04.1~ppa2
charm-tools 2.1.9

I am using: Ubuntu 16.04 LTS

Issue/Feature

I expect/expected the following

charm proof should check that resource names are valid.

What I got

I spent some time trying to debug a mysteriously-failing juju deploy. Eventually I found the following log entry:

2017-01-17 12:17:01 ERROR juju.worker.dependency engine.go:539 "mgo-txn-resumer" manifold worker returned unexpected error: cannot resume transactions: The dotted field 'launchpad.tar.gz' in 'meta.resources.launchpad.tar.gz' is not valid for storage.

The charm's metadata.yaml was as follows:

name: launchpad-importd
summary: Launchpad code import daemon
description: |
    A Launchpad code import daemon.
tags:
    - application_development
maintainer: Colin Watson <cjwatson@canonical.com>
subordinate: false
series:
    - xenial
resources:
    launchpad.tar.gz:
        type: file
        filename: launchpad.tar.gz
        description: The Launchpad source code.
min-juju-version: 2.0.0

However, charm proof only emitted the following informative message, with no errors:

I: No icon.svg file.

I think that charm proof should have told me that the resource name I'd chosen was invalid.