Cumulus should tell you when passing string instead of array to "depends"

[radeksimko]

Following template:

default:
  region: eu-west-1
  stacks:
    networking:
      cf_template: networking.json
      depends:
    computing:
      cf_template: computing.json
      depends: networking

end up in really unhelpful error:

CRITICAL:cumulus.MegaStack:Could not resolve dependancy order. Either circular dependancy or dependancy on stack not in yaml file.

It took me almost an hour to find out that depends expects an array, not a string, which is why I think that cumulus should first check what's being passed from the YAML template (string or array) and then show helpful error if it's a string.

btw. dependancy is spelled as dependency in modern english. http://en.wiktionary.org/wiki/dependancy