gracefully handle wrong pipeline component format in config

[sentry-io]

Sentry Issue: RASA-OPEN-SOURCE-3DY

Stack Trace

AttributeError: 'str' object has no attribute 'get'
(10 additional frame(s) were not displayed)
...
  File "rasa/train.py", line 818, in _train_nlu_with_validated_data
    **additional_arguments,
  File "rasa/nlu/train.py", line 98, in train
    nlu_config, component_builder, model_to_finetune=model_to_finetune
  File "rasa/nlu/model.py", line 158, in __init__
    components.validate_requirements(cfg.component_names)
  File "rasa/nlu/config.py", line 146, in component_names
    return [c.get("name") for c in self.pipeline]
  File "rasa/nlu/config.py", line 146, in <listcomp>
    return [c.get("name") for c in self.pipeline]

Further Information

This happens if the entry for a pipeline is not a dict as expected, e.g:

pipeline:
- "hi, I'm a string and not a dict"
- name: "WhiteSpaceTokenizer"

Potential Solutions

• Make the schema stricter (it's a joke of a schema at the moment)
• add a check in the code which checks it's a dict and throws a RasaException with a helpful error message
• catch exception and wrap in RasaException

[sentry-io]

Sentry issue: RASA-OPEN-SOURCE-659