A better error message when an YAML file malformed

[bkielbasa]

🐛 Proposal

I found it difficult to find where exactly I made a mistake while editing multiple YAML files. When I make a mistake I get the following (or similar) error message

Binding opctl API to 127.0.0.1:42224


-
  Error(s):
    - error converting YAML to JSON: yaml: line 38: could not find expected ':'
-

The problem is that there's no way to find out where exactly the problem is what makes it even harder to debug.