Return the spec (URL, package spec, file, etc) for a named resource.

def resource_spec(opts):
    """
    Return the spec (URL, package spec, file, etc) for a named resource.
    """
    resources = _load(opts.resources, opts.output_dir)
    if opts.resource_name not in resources:
        sys.stderr.write('Invalid resource name: {}\n'.format(opts.resource_name))
        return 1
    print(resources[opts.resource_name].spec)