rasa: misleading error message with `actions` folder

if you run rasa run actions with no actions.py file, you get a helpful:

(rasa) ellas-mbp-2:formbot erohmensing$ rasa run actions
The path 'actions.py' does not exist. Please make sure to use the default location ('actions') or specify it with '--action'.

However, if your actions files are in an actions folder, you get this confusing message:

(rasa) ellas-mbp-2:formbot erohmensing$ rasa run actions
No model found. Train a model before running the server using `rasa train`.

Either this should be fixed, or we should just support loading files from an actions directory as well as from actions.py.