Validation errors should be improved

[Pennycook]

Feature/behavior summary

Functions like util._load_json and util._load_toml currently throw exceptions that contain information from jsonschema. We intercept these (typically by catching BaseException) in order to throw another exception containing details about which type of file failed validation.

Request attributes

• [X] Would this be a refactor of existing code?
• [ ] Does this proposal require new package dependencies?
• [X] Would this change break backwards compatibility?

Related issues

No response

Solution description

We should adopt a new design of these validation routines that enables loading a JSON or TOML file to directly throw an exception containing meaningful information.

Additional notes

No response