Fix JSON validation to accomodate JSONField data that looks like a python literal.
Sometimes, our JSONField data will have embedded unicode markers for keys,

which isn't part of JSON but sometimes happens with python's json

serialization. We handle this in the field by using literal_eval on the data,

but the validator for form fields wasn't doing the same. I've extracted this

functionality into a method and used it for both the database field and the

validator.

Hit "save" on the reviewboard repository admin form when the extra_data field

had unicode markers for keys in the dictionary. Saw that it validated properly.